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	$152.52	9.176%	$166.5152	$166.52	$166.50	$166.50
Purchase #2	$120.83	13.277%	$136.8726	$136.87	$136.85	$136.90
Purchase #3	$144.63	9.280%	$158.0517	$158.05	$158.05	$158.10
Purchase #4	$82.56	3.251%	$85.244	$85.24	$85.25	$85.20
Purchase #5	$89.25	7.862%	$96.2668	$96.27	$96.25	$96.30
Purchase #6	$199.28	8.399%	$216.0175	$216.02	$216.00	$216.00
Purchase #7	$214.78	10.316%	$236.9367	$236.94	$236.95	$236.90
7 purchase totals =	$1,003.85		$1,095.9045	$1,095.91	$1,095.85	$1,095.90