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	$158.31	5.414%	$166.8809	$166.88	$166.90	$166.90
Purchase #2	$113.76	8.508%	$123.4387	$123.44	$123.45	$123.40
Purchase #3	$72.70	3.334%	$75.1238	$75.12	$75.10	$75.10
Purchase #4	$158.68	4.436%	$165.719	$165.72	$165.70	$165.70
Purchase #5	$207.41	3.744%	$215.1754	$215.18	$215.20	$215.20
Purchase #6	$100.38	10.821%	$111.2421	$111.24	$111.25	$111.20
Purchase #7	$172.33	3.364%	$178.1272	$178.13	$178.15	$178.10
7 purchase totals =	$983.57		$1,035.7071	$1,035.71	$1,035.75	$1,035.60