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	$171.37	11.380%	$190.8719	$190.87	$190.85	$190.90
Purchase #2	$5.82	3.823%	$6.0425	$6.04	$6.05	$6.00
Purchase #3	$129.86	7.519%	$139.6242	$139.62	$139.60	$139.60
Purchase #4	$223.83	9.565%	$245.2393	$245.24	$245.25	$245.20
Purchase #5	$148.37	4.501%	$155.0481	$155.05	$155.05	$155.00
Purchase #6	$56.93	9.185%	$62.159	$62.16	$62.15	$62.20
Purchase #7	$242.52	12.301%	$272.3524	$272.35	$272.35	$272.40
7 purchase totals =	$978.70		$1,071.3374	$1,071.33	$1,071.30	$1,071.30