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	$118.82	9.872%	$130.5499	$130.55	$130.55	$130.50
Purchase #2	$140.96	4.369%	$147.1185	$147.12	$147.10	$147.10
Purchase #3	$140.63	10.865%	$155.9094	$155.91	$155.90	$155.90
Purchase #4	$35.89	9.122%	$39.1639	$39.16	$39.15	$39.20
Purchase #5	$91.92	13.271%	$104.1187	$104.12	$104.10	$104.10
Purchase #6	$118.45	4.151%	$123.3669	$123.37	$123.35	$123.40
Purchase #7	$193.86	3.596%	$200.8312	$200.83	$200.85	$200.80
7 purchase totals =	$840.53		$901.0585	$901.06	$901.00	$901.00