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	$41.44	4.868%	$43.4573	$43.46	$43.45	$43.50
Purchase #2	$167.38	4.823%	$175.4527	$175.45	$175.45	$175.50
Purchase #3	$64.64	10.685%	$71.5468	$71.55	$71.55	$71.50
Purchase #4	$29.34	11.644%	$32.7563	$32.76	$32.75	$32.80
Purchase #5	$30.69	8.551%	$33.3143	$33.31	$33.30	$33.30
Purchase #6	$92.78	7.345%	$99.5947	$99.59	$99.60	$99.60
Purchase #7	$63.84	6.866%	$68.2233	$68.22	$68.20	$68.20
7 purchase totals =	$490.11		$524.3454	$524.34	$524.30	$524.40