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	$165.96	10.459%	$183.3178	$183.32	$183.30	$183.30
Purchase #2	$151.54	4.720%	$158.6927	$158.69	$158.70	$158.70
Purchase #3	$196.80	13.325%	$223.0236	$223.02	$223.00	$223.00
Purchase #4	$63.60	13.174%	$71.9787	$71.98	$72.00	$72.00
Purchase #5	$175.36	10.368%	$193.5413	$193.54	$193.55	$193.50
Purchase #6	$127.98	8.548%	$138.9197	$138.92	$138.90	$138.90
Purchase #7	$142.74	3.281%	$147.4233	$147.42	$147.40	$147.40
7 purchase totals =	$1,023.98		$1,116.8971	$1,116.89	$1,116.85	$1,116.80