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	$194.85	7.327%	$209.1267	$209.13	$209.15	$209.10
Purchase #2	$18.35	12.591%	$20.6604	$20.66	$20.65	$20.70
Purchase #3	$148.59	3.718%	$154.1146	$154.11	$154.10	$154.10
Purchase #4	$151.57	10.513%	$167.5046	$167.50	$167.50	$167.50
Purchase #5	$29.46	13.229%	$33.3573	$33.36	$33.35	$33.40
Purchase #6	$128.74	4.651%	$134.7277	$134.73	$134.75	$134.70
Purchase #7	$84.39	5.822%	$89.3032	$89.30	$89.30	$89.30
7 purchase totals =	$755.95		$808.7945	$808.79	$808.80	$808.80