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	$64.55	11.843%	$72.1947	$72.19	$72.20	$72.20
Purchase #2	$48.36	9.711%	$53.0562	$53.06	$53.05	$53.10
Purchase #3	$12.73	3.158%	$13.132	$13.13	$13.15	$13.10
Purchase #4	$6.83	7.159%	$7.319	$7.32	$7.30	$7.30
Purchase #5	$203.53	8.663%	$221.1618	$221.16	$221.15	$221.20
Purchase #6	$177.90	12.683%	$200.4631	$200.46	$200.45	$200.50
Purchase #7	$172.38	5.154%	$181.2645	$181.26	$181.25	$181.30
7 purchase totals =	$686.28		$748.5913	$748.58	$748.55	$748.70