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	$115.56	10.815%	$128.0578	$128.06	$128.05	$128.10
Purchase #2	$124.31	5.199%	$130.7729	$130.77	$130.75	$130.80
Purchase #3	$155.53	10.308%	$171.562	$171.56	$171.55	$171.60
Purchase #4	$24.48	4.650%	$25.6183	$25.62	$25.60	$25.60
Purchase #5	$96.25	4.817%	$100.8864	$100.89	$100.90	$100.90
Purchase #6	$26.62	6.198%	$28.2699	$28.27	$28.25	$28.30
Purchase #7	$61.90	11.186%	$68.8241	$68.82	$68.80	$68.80
7 purchase totals =	$604.65		$653.9914	$653.99	$653.90	$654.10