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	$51.80	3.721%	$53.7275	$53.73	$53.75	$53.70
Purchase #2	$51.66	3.504%	$53.4702	$53.47	$53.45	$53.50
Purchase #3	$211.96	5.275%	$223.1409	$223.14	$223.15	$223.10
Purchase #4	$220.31	7.204%	$236.1811	$236.18	$236.20	$236.20
Purchase #5	$125.72	12.631%	$141.5997	$141.60	$141.60	$141.60
Purchase #6	$233.91	6.834%	$249.8954	$249.90	$249.90	$249.90
Purchase #7	$187.95	6.605%	$200.3641	$200.36	$200.35	$200.40
7 purchase totals =	$1,083.31		$1,158.3789	$1,158.38	$1,158.40	$1,158.40