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	$88.58	10.777%	$98.1263	$98.13	$98.15	$98.10
Purchase #2	$98.35	9.851%	$108.0385	$108.04	$108.05	$108.00
Purchase #3	$111.25	13.225%	$125.9628	$125.96	$125.95	$126.00
Purchase #4	$88.31	3.113%	$91.0591	$91.06	$91.05	$91.10
Purchase #5	$62.27	8.489%	$67.5561	$67.56	$67.55	$67.60
Purchase #6	$54.94	8.352%	$59.5286	$59.53	$59.55	$59.50
Purchase #7	$213.33	4.391%	$222.6973	$222.70	$222.70	$222.70
7 purchase totals =	$717.03		$772.9687	$772.98	$773.00	$773.00