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	$205.76	11.361%	$229.1364	$229.14	$229.15	$229.10
Purchase #2	$162.37	6.313%	$172.6204	$172.62	$172.60	$172.60
Purchase #3	$51.45	7.213%	$55.1611	$55.16	$55.15	$55.20
Purchase #4	$27.96	12.704%	$31.512	$31.51	$31.50	$31.50
Purchase #5	$169.37	13.163%	$191.6642	$191.66	$191.65	$191.70
Purchase #6	$80.66	13.448%	$91.5072	$91.51	$91.50	$91.50
Purchase #7	$245.63	10.158%	$270.5811	$270.58	$270.60	$270.60
7 purchase totals =	$943.20		$1,042.1824	$1,042.18	$1,042.15	$1,042.20