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	$141.39	8.845%	$153.8959	$153.90	$153.90	$153.90
Purchase #2	$144.63	3.714%	$150.0016	$150.00	$150.00	$150.00
Purchase #3	$127.79	10.304%	$140.9575	$140.96	$140.95	$141.00
Purchase #4	$133.86	12.760%	$150.9405	$150.94	$150.95	$150.90
Purchase #5	$115.62	12.275%	$129.8124	$129.81	$129.80	$129.80
Purchase #6	$35.41	6.843%	$37.8331	$37.83	$37.85	$37.80
Purchase #7	$222.29	3.841%	$230.8282	$230.83	$230.85	$230.80
7 purchase totals =	$920.99		$994.2692	$994.27	$994.30	$994.20