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	$165.86	7.710%	$178.6478	$178.65	$178.65	$178.60
Purchase #2	$222.35	10.399%	$245.4722	$245.47	$245.45	$245.50
Purchase #3	$27.89	9.135%	$30.4378	$30.44	$30.45	$30.40
Purchase #4	$24.69	11.674%	$27.5723	$27.57	$27.55	$27.60
Purchase #5	$79.63	12.808%	$89.829	$89.83	$89.85	$89.80
Purchase #6	$243.38	3.320%	$251.4602	$251.46	$251.45	$251.50
Purchase #7	$35.59	11.733%	$39.7658	$39.77	$39.75	$39.80
7 purchase totals =	$799.39		$863.1851	$863.19	$863.15	$863.20