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	$154.32	9.773%	$169.4017	$169.40	$169.40	$169.40
Purchase #2	$59.70	5.364%	$62.9023	$62.90	$62.90	$62.90
Purchase #3	$167.57	12.195%	$188.0052	$188.01	$188.00	$188.00
Purchase #4	$110.70	7.674%	$119.1951	$119.20	$119.20	$119.20
Purchase #5	$112.59	11.661%	$125.7191	$125.72	$125.70	$125.70
Purchase #6	$186.39	12.607%	$209.8882	$209.89	$209.90	$209.90
Purchase #7	$61.42	9.341%	$67.1572	$67.16	$67.15	$67.20
7 purchase totals =	$852.69		$942.2688	$942.28	$942.25	$942.30