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	$99.45	4.190%	$103.617	$103.62	$103.60	$103.60
Purchase #2	$195.40	3.742%	$202.7119	$202.71	$202.70	$202.70
Purchase #3	$106.75	4.240%	$111.2762	$111.28	$111.30	$111.30
Purchase #4	$213.30	9.430%	$233.4142	$233.41	$233.40	$233.40
Purchase #5	$67.46	5.669%	$71.2843	$71.28	$71.30	$71.30
Purchase #6	$250.33	13.873%	$285.0583	$285.06	$285.05	$285.10
Purchase #7	$59.47	7.321%	$63.8238	$63.82	$63.80	$63.80
7 purchase totals =	$992.16		$1,071.1857	$1,071.18	$1,071.15	$1,071.20