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	$216.91	3.218%	$223.8902	$223.89	$223.90	$223.90
Purchase #2	$229.61	13.778%	$261.2457	$261.25	$261.25	$261.20
Purchase #3	$31.88	13.656%	$36.2335	$36.23	$36.25	$36.20
Purchase #4	$176.36	8.866%	$191.9961	$192.00	$192.00	$192.00
Purchase #5	$162.79	6.466%	$173.316	$173.32	$173.30	$173.30
Purchase #6	$89.42	9.814%	$98.1957	$98.20	$98.20	$98.20
Purchase #7	$128.85	10.778%	$142.7375	$142.74	$142.75	$142.70
7 purchase totals =	$1,035.82		$1,127.6147	$1,127.63	$1,127.65	$1,127.50