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	$113.48	9.419%	$124.1687	$124.17	$124.15	$124.20
Purchase #2	$166.81	4.235%	$173.8744	$173.87	$173.85	$173.90
Purchase #3	$126.26	9.124%	$137.78	$137.78	$137.80	$137.80
Purchase #4	$229.76	11.463%	$256.0974	$256.10	$256.10	$256.10
Purchase #5	$215.48	5.145%	$226.5664	$226.57	$226.55	$226.60
Purchase #6	$14.43	9.588%	$15.8135	$15.81	$15.80	$15.80
Purchase #7	$73.50	12.773%	$82.8882	$82.89	$82.90	$82.90
7 purchase totals =	$939.72		$1,017.1886	$1,017.19	$1,017.15	$1,017.30