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	$70.29	4.560%	$73.4952	$73.50	$73.50	$73.50
Purchase #2	$151.39	13.164%	$171.319	$171.32	$171.30	$171.30
Purchase #3	$111.70	5.141%	$117.4425	$117.44	$117.45	$117.40
Purchase #4	$147.62	6.870%	$157.7615	$157.76	$157.75	$157.80
Purchase #5	$28.62	12.687%	$32.251	$32.25	$32.25	$32.30
Purchase #6	$42.56	13.535%	$48.3205	$48.32	$48.30	$48.30
Purchase #7	$10.33	12.820%	$11.6543	$11.65	$11.65	$11.70
7 purchase totals =	$562.51		$612.2440	$612.24	$612.20	$612.30