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	$68.56	5.300%	$72.1937	$72.19	$72.20	$72.20
Purchase #2	$86.56	11.732%	$96.7152	$96.72	$96.70	$96.70
Purchase #3	$35.72	12.238%	$40.0914	$40.09	$40.10	$40.10
Purchase #4	$53.54	10.529%	$59.1772	$59.18	$59.20	$59.20
Purchase #5	$46.42	3.671%	$48.1241	$48.12	$48.10	$48.10
Purchase #6	$169.54	8.654%	$184.212	$184.21	$184.20	$184.20
Purchase #7	$183.84	5.613%	$194.1589	$194.16	$194.15	$194.20
7 purchase totals =	$644.18		$694.6725	$694.67	$694.65	$694.70