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	$147.89	11.158%	$164.3916	$164.39	$164.40	$164.40
Purchase #2	$177.78	12.177%	$199.4283	$199.43	$199.45	$199.40
Purchase #3	$94.53	7.439%	$101.5621	$101.56	$101.55	$101.60
Purchase #4	$216.37	5.805%	$228.9303	$228.93	$228.95	$228.90
Purchase #5	$165.25	4.119%	$172.0566	$172.06	$172.05	$172.10
Purchase #6	$41.66	3.109%	$42.9552	$42.96	$42.95	$43.00
Purchase #7	$14.41	11.829%	$16.1146	$16.11	$16.10	$16.10
7 purchase totals =	$857.89		$925.4387	$925.44	$925.45	$925.50