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	$56.75	11.555%	$63.3075	$63.31	$63.30	$63.30
Purchase #2	$83.93	7.399%	$90.14	$90.14	$90.15	$90.10
Purchase #3	$154.38	7.493%	$165.9477	$165.95	$165.95	$165.90
Purchase #4	$180.53	8.521%	$195.913	$195.91	$195.90	$195.90
Purchase #5	$185.86	11.601%	$207.4216	$207.42	$207.40	$207.40
Purchase #6	$205.57	8.257%	$222.5439	$222.54	$222.55	$222.50
Purchase #7	$69.62	12.663%	$78.436	$78.44	$78.45	$78.40
7 purchase totals =	$936.64		$1,023.7097	$1,023.71	$1,023.70	$1,023.50