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	$184.72	6.169%	$196.1154	$196.12	$196.10	$196.10
Purchase #2	$79.96	12.141%	$89.6679	$89.67	$89.65	$89.70
Purchase #3	$223.78	5.575%	$236.2557	$236.26	$236.25	$236.30
Purchase #4	$87.57	9.870%	$96.2132	$96.21	$96.20	$96.20
Purchase #5	$150.34	5.186%	$158.1366	$158.14	$158.15	$158.10
Purchase #6	$233.49	5.157%	$245.5311	$245.53	$245.55	$245.50
Purchase #7	$131.86	7.607%	$141.8906	$141.89	$141.90	$141.90
7 purchase totals =	$1,091.72		$1,163.8105	$1,163.82	$1,163.80	$1,163.80