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	$214.43	3.611%	$222.1731	$222.17	$222.15	$222.20
Purchase #2	$129.28	3.732%	$134.1047	$134.10	$134.10	$134.10
Purchase #3	$180.89	10.746%	$200.3284	$200.33	$200.35	$200.30
Purchase #4	$130.35	8.255%	$141.1104	$141.11	$141.10	$141.10
Purchase #5	$94.34	9.298%	$103.1117	$103.11	$103.10	$103.10
Purchase #6	$135.57	4.159%	$141.2084	$141.21	$141.20	$141.20
Purchase #7	$69.91	6.234%	$74.2682	$74.27	$74.25	$74.30
7 purchase totals =	$954.77		$1,016.3049	$1,016.30	$1,016.25	$1,016.30