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	$149.29	11.744%	$166.8226	$166.82	$166.80	$166.80
Purchase #2	$167.69	11.149%	$186.3858	$186.39	$186.40	$186.40
Purchase #3	$59.33	11.705%	$66.2746	$66.27	$66.25	$66.30
Purchase #4	$84.72	9.843%	$93.059	$93.06	$93.05	$93.10
Purchase #5	$136.94	10.312%	$151.0613	$151.06	$151.05	$151.10
Purchase #6	$215.79	13.581%	$245.0964	$245.10	$245.10	$245.10
Purchase #7	$220.89	9.757%	$242.4422	$242.44	$242.45	$242.40
7 purchase totals =	$1,034.65		$1,151.1419	$1,151.14	$1,151.10	$1,151.20