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	$63.87	13.479%	$72.479	$72.48	$72.50	$72.50
Purchase #2	$10.81	13.759%	$12.2973	$12.30	$12.30	$12.30
Purchase #3	$96.95	12.408%	$108.9796	$108.98	$109.00	$109.00
Purchase #4	$81.28	9.844%	$89.2812	$89.28	$89.30	$89.30
Purchase #5	$27.45	10.418%	$30.3097	$30.31	$30.30	$30.30
Purchase #6	$198.77	12.258%	$223.1352	$223.14	$223.15	$223.10
Purchase #7	$175.47	10.391%	$193.7031	$193.70	$193.70	$193.70
7 purchase totals =	$654.60		$730.1851	$730.19	$730.25	$730.20