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	$248.49	8.623%	$269.9173	$269.92	$269.90	$269.90
Purchase #2	$200.76	9.510%	$219.8523	$219.85	$219.85	$219.90
Purchase #3	$37.73	13.644%	$42.8779	$42.88	$42.90	$42.90
Purchase #4	$248.54	11.589%	$277.3433	$277.34	$277.35	$277.30
Purchase #5	$152.46	9.305%	$166.6464	$166.65	$166.65	$166.60
Purchase #6	$172.97	13.328%	$196.0234	$196.02	$196.00	$196.00
Purchase #7	$13.91	3.525%	$14.4003	$14.40	$14.40	$14.40
7 purchase totals =	$1,074.86		$1,187.0609	$1,187.06	$1,187.05	$1,187.00