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	$191.74	3.730%	$198.8919	$198.89	$198.90	$198.90
Purchase #2	$140.41	6.439%	$149.451	$149.45	$149.45	$149.50
Purchase #3	$73.48	7.440%	$78.9469	$78.95	$78.95	$78.90
Purchase #4	$67.98	4.253%	$70.8712	$70.87	$70.85	$70.90
Purchase #5	$220.38	5.321%	$232.1064	$232.11	$232.10	$232.10
Purchase #6	$133.70	12.567%	$150.5021	$150.50	$150.50	$150.50
Purchase #7	$118.87	13.815%	$135.2919	$135.29	$135.30	$135.30
7 purchase totals =	$946.56		$1,016.0614	$1,016.06	$1,016.05	$1,016.10