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	$152.96	9.518%	$167.5187	$167.52	$167.50	$167.50
Purchase #2	$240.33	6.751%	$256.5547	$256.55	$256.55	$256.60
Purchase #3	$228.88	9.457%	$250.5252	$250.53	$250.55	$250.50
Purchase #4	$110.82	4.812%	$116.1527	$116.15	$116.15	$116.20
Purchase #5	$232.93	9.447%	$254.9349	$254.93	$254.95	$254.90
Purchase #6	$128.49	6.226%	$136.4898	$136.49	$136.50	$136.50
Purchase #7	$143.56	13.444%	$162.8602	$162.86	$162.85	$162.90
7 purchase totals =	$1,237.97		$1,345.0362	$1,345.03	$1,345.05	$1,345.10