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	$154.39	12.770%	$174.1056	$174.11	$174.10	$174.10
Purchase #2	$102.75	8.128%	$111.1015	$111.10	$111.10	$111.10
Purchase #3	$148.78	3.412%	$153.8564	$153.86	$153.85	$153.90
Purchase #4	$41.73	12.375%	$46.8941	$46.89	$46.90	$46.90
Purchase #5	$150.97	13.547%	$171.4219	$171.42	$171.40	$171.40
Purchase #6	$107.94	10.502%	$119.2759	$119.28	$119.30	$119.30
Purchase #7	$211.51	7.571%	$227.5234	$227.52	$227.50	$227.50
7 purchase totals =	$918.07		$1,004.1788	$1,004.18	$1,004.15	$1,004.20