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	$57.44	5.213%	$60.4343	$60.43	$60.45	$60.40
Purchase #2	$190.82	6.156%	$202.5669	$202.57	$202.55	$202.60
Purchase #3	$116.64	9.125%	$127.2834	$127.28	$127.30	$127.30
Purchase #4	$145.62	6.826%	$155.56	$155.56	$155.55	$155.60
Purchase #5	$107.40	4.714%	$112.4628	$112.46	$112.45	$112.50
Purchase #6	$63.50	11.503%	$70.8044	$70.80	$70.80	$70.80
Purchase #7	$242.73	12.640%	$273.4111	$273.41	$273.40	$273.40
7 purchase totals =	$924.15		$1,002.5229	$1,002.51	$1,002.50	$1,002.60