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	$188.46	12.819%	$212.6187	$212.62	$212.60	$212.60
Purchase #2	$100.94	10.398%	$111.4357	$111.44	$111.45	$111.40
Purchase #3	$213.29	12.625%	$240.2179	$240.22	$240.20	$240.20
Purchase #4	$27.26	13.393%	$30.9109	$30.91	$30.90	$30.90
Purchase #5	$71.75	3.846%	$74.5095	$74.51	$74.50	$74.50
Purchase #6	$101.33	12.526%	$114.0226	$114.02	$114.00	$114.00
Purchase #7	$83.93	9.437%	$91.8505	$91.85	$91.85	$91.90
7 purchase totals =	$786.96		$875.5658	$875.57	$875.50	$875.50