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	$184.90	6.408%	$196.7484	$196.75	$196.75	$196.70
Purchase #2	$105.34	4.160%	$109.7221	$109.72	$109.70	$109.70
Purchase #3	$53.70	7.819%	$57.8988	$57.90	$57.90	$57.90
Purchase #4	$119.25	4.246%	$124.3134	$124.31	$124.30	$124.30
Purchase #5	$37.76	5.715%	$39.918	$39.92	$39.90	$39.90
Purchase #6	$78.58	12.872%	$88.6948	$88.69	$88.70	$88.70
Purchase #7	$93.55	3.291%	$96.6287	$96.63	$96.65	$96.60
7 purchase totals =	$673.08		$713.9242	$713.92	$713.90	$713.80