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	$173.37	7.202%	$185.8561	$185.86	$185.85	$185.90
Purchase #2	$248.55	13.428%	$281.9253	$281.93	$281.95	$281.90
Purchase #3	$15.97	13.583%	$18.1392	$18.14	$18.15	$18.10
Purchase #4	$61.71	12.331%	$69.3195	$69.32	$69.30	$69.30
Purchase #5	$225.36	6.743%	$240.556	$240.56	$240.55	$240.60
Purchase #6	$31.35	4.123%	$32.6426	$32.64	$32.65	$32.60
Purchase #7	$79.38	8.486%	$86.1162	$86.12	$86.10	$86.10
7 purchase totals =	$835.69		$914.5549	$914.57	$914.55	$914.50