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	$181.35	3.704%	$188.0672	$188.07	$188.05	$188.10
Purchase #2	$196.27	5.200%	$206.476	$206.48	$206.50	$206.50
Purchase #3	$103.79	11.466%	$115.6906	$115.69	$115.70	$115.70
Purchase #4	$21.57	4.587%	$22.5594	$22.56	$22.55	$22.60
Purchase #5	$85.88	4.268%	$89.5454	$89.55	$89.55	$89.50
Purchase #6	$20.76	13.136%	$23.487	$23.49	$23.50	$23.50
Purchase #7	$74.25	5.203%	$78.1132	$78.11	$78.10	$78.10
7 purchase totals =	$683.87		$723.9388	$723.95	$723.95	$724.00