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	$115.85	7.412%	$124.4368	$124.44	$124.45	$124.40
Purchase #2	$247.99	3.349%	$256.2952	$256.30	$256.30	$256.30
Purchase #3	$155.33	4.847%	$162.8588	$162.86	$162.85	$162.90
Purchase #4	$99.27	9.217%	$108.4197	$108.42	$108.40	$108.40
Purchase #5	$120.58	5.366%	$127.0503	$127.05	$127.05	$127.10
Purchase #6	$93.44	3.661%	$96.8608	$96.86	$96.85	$96.90
Purchase #7	$92.69	13.802%	$105.4831	$105.48	$105.50	$105.50
7 purchase totals =	$925.15		$981.4047	$981.41	$981.40	$981.50