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	$221.32	11.653%	$247.1104	$247.11	$247.10	$247.10
Purchase #2	$82.89	4.836%	$86.8986	$86.90	$86.90	$86.90
Purchase #3	$70.92	9.471%	$77.6368	$77.64	$77.65	$77.60
Purchase #4	$78.75	13.702%	$89.5403	$89.54	$89.55	$89.50
Purchase #5	$179.62	11.751%	$200.7271	$200.73	$200.75	$200.70
Purchase #6	$177.72	7.666%	$191.344	$191.34	$191.35	$191.30
Purchase #7	$210.58	8.795%	$229.1005	$229.10	$229.10	$229.10
7 purchase totals =	$1,021.80		$1,122.3577	$1,122.36	$1,122.40	$1,122.20