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	$194.62	6.819%	$207.8911	$207.89	$207.90	$207.90
Purchase #2	$50.88	6.300%	$54.0854	$54.09	$54.10	$54.10
Purchase #3	$7.49	3.619%	$7.7611	$7.76	$7.75	$7.80
Purchase #4	$100.89	13.186%	$114.1934	$114.19	$114.20	$114.20
Purchase #5	$198.76	12.256%	$223.12	$223.12	$223.10	$223.10
Purchase #6	$13.69	13.543%	$15.544	$15.54	$15.55	$15.50
Purchase #7	$17.88	5.281%	$18.8242	$18.82	$18.80	$18.80
7 purchase totals =	$584.21		$641.4192	$641.41	$641.40	$641.40