Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$156.30	5.724%	$165.2466	$165.25	$165.25	$165.20
Purchase #2	$149.26	11.793%	$166.8622	$166.86	$166.85	$166.90
Purchase #3	$154.70	11.662%	$172.7411	$172.74	$172.75	$172.70
Purchase #4	$155.34	8.713%	$168.8748	$168.87	$168.85	$168.90
Purchase #5	$178.51	11.833%	$199.6331	$199.63	$199.65	$199.60
Purchase #6	$105.77	3.169%	$109.1219	$109.12	$109.10	$109.10
Purchase #7	$176.25	9.174%	$192.4192	$192.42	$192.40	$192.40
7 purchase totals =	$1,076.13		$1,174.8989	$1,174.89	$1,174.85	$1,174.80