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	$215.33	8.859%	$234.4061	$234.41	$234.40	$234.40
Purchase #2	$164.39	4.571%	$171.9043	$171.90	$171.90	$171.90
Purchase #3	$142.76	11.245%	$158.8134	$158.81	$158.80	$158.80
Purchase #4	$151.90	3.251%	$156.8383	$156.84	$156.85	$156.80
Purchase #5	$37.81	13.562%	$42.9378	$42.94	$42.95	$42.90
Purchase #6	$43.39	6.343%	$46.1422	$46.14	$46.15	$46.10
Purchase #7	$192.76	13.467%	$218.719	$218.72	$218.70	$218.70
7 purchase totals =	$948.34		$1,029.7611	$1,029.76	$1,029.75	$1,029.60