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	$188.73	5.393%	$198.9082	$198.91	$198.90	$198.90
Purchase #2	$196.86	13.289%	$223.0207	$223.02	$223.00	$223.00
Purchase #3	$41.42	3.316%	$42.7935	$42.79	$42.80	$42.80
Purchase #4	$169.80	8.160%	$183.6557	$183.66	$183.65	$183.70
Purchase #5	$53.68	12.624%	$60.4566	$60.46	$60.45	$60.50
Purchase #6	$116.36	13.139%	$131.6485	$131.65	$131.65	$131.60
Purchase #7	$36.77	3.459%	$38.0419	$38.04	$38.05	$38.00
7 purchase totals =	$803.62		$878.5251	$878.53	$878.50	$878.50