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	$182.33	5.233%	$191.8713	$191.87	$191.85	$191.90
Purchase #2	$31.70	12.615%	$35.699	$35.70	$35.70	$35.70
Purchase #3	$76.40	9.458%	$83.6259	$83.63	$83.65	$83.60
Purchase #4	$102.70	6.187%	$109.054	$109.05	$109.05	$109.10
Purchase #5	$187.81	12.766%	$211.7858	$211.79	$211.80	$211.80
Purchase #6	$145.40	6.481%	$154.8234	$154.82	$154.80	$154.80
Purchase #7	$194.58	11.267%	$216.5033	$216.50	$216.50	$216.50
7 purchase totals =	$920.92		$1,003.3627	$1,003.36	$1,003.35	$1,003.40