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	$153.96	6.834%	$164.4816	$164.48	$164.50	$164.50
Purchase #2	$141.84	5.822%	$150.0979	$150.10	$150.10	$150.10
Purchase #3	$101.66	4.199%	$105.9287	$105.93	$105.95	$105.90
Purchase #4	$151.27	4.860%	$158.6217	$158.62	$158.60	$158.60
Purchase #5	$106.81	6.442%	$113.6907	$113.69	$113.70	$113.70
Purchase #6	$112.30	13.394%	$127.3415	$127.34	$127.35	$127.30
Purchase #7	$154.70	7.173%	$165.7966	$165.80	$165.80	$165.80
7 purchase totals =	$922.54		$985.9587	$985.96	$986.00	$985.90