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	$50.80	5.794%	$53.7434	$53.74	$53.75	$53.70
Purchase #2	$239.45	7.363%	$257.0807	$257.08	$257.10	$257.10
Purchase #3	$71.86	9.112%	$78.4079	$78.41	$78.40	$78.40
Purchase #4	$147.84	13.169%	$167.309	$167.31	$167.30	$167.30
Purchase #5	$52.98	3.657%	$54.9175	$54.92	$54.90	$54.90
Purchase #6	$125.53	9.795%	$137.8257	$137.83	$137.85	$137.80
Purchase #7	$12.43	3.488%	$12.8636	$12.86	$12.85	$12.90
7 purchase totals =	$700.89		$762.1478	$762.15	$762.15	$762.10