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	$98.59	6.127%	$104.6306	$104.63	$104.65	$104.60
Purchase #2	$165.56	13.344%	$187.6523	$187.65	$187.65	$187.70
Purchase #3	$192.87	6.251%	$204.9263	$204.93	$204.95	$204.90
Purchase #4	$219.63	10.245%	$242.1311	$242.13	$242.15	$242.10
Purchase #5	$109.27	3.697%	$113.3097	$113.31	$113.30	$113.30
Purchase #6	$98.88	12.731%	$111.4684	$111.47	$111.45	$111.50
Purchase #7	$170.75	3.315%	$176.4104	$176.41	$176.40	$176.40
7 purchase totals =	$1,055.55		$1,140.5288	$1,140.53	$1,140.55	$1,140.50