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	$96.64	11.614%	$107.8638	$107.86	$107.85	$107.90
Purchase #2	$131.79	9.741%	$144.6277	$144.63	$144.65	$144.60
Purchase #3	$170.64	10.486%	$188.5333	$188.53	$188.55	$188.50
Purchase #4	$180.99	10.332%	$199.6899	$199.69	$199.70	$199.70
Purchase #5	$123.36	3.133%	$127.2249	$127.22	$127.20	$127.20
Purchase #6	$80.60	11.551%	$89.9101	$89.91	$89.90	$89.90
Purchase #7	$250.95	5.664%	$265.1638	$265.16	$265.15	$265.20
7 purchase totals =	$1,034.97		$1,123.0135	$1,123.00	$1,123.00	$1,123.00