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	$181.72	4.521%	$189.9356	$189.94	$189.95	$189.90
Purchase #2	$244.95	9.484%	$268.1811	$268.18	$268.20	$268.20
Purchase #3	$98.46	12.709%	$110.9733	$110.97	$110.95	$111.00
Purchase #4	$58.63	7.306%	$62.9135	$62.91	$62.90	$62.90
Purchase #5	$131.60	11.380%	$146.5761	$146.58	$146.60	$146.60
Purchase #6	$89.64	12.699%	$101.0234	$101.02	$101.00	$101.00
Purchase #7	$122.76	11.159%	$136.4588	$136.46	$136.45	$136.50
7 purchase totals =	$927.76		$1,016.0618	$1,016.06	$1,016.05	$1,016.10