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	$107.76	11.465%	$120.1147	$120.11	$120.10	$120.10
Purchase #2	$66.94	5.384%	$70.544	$70.54	$70.55	$70.50
Purchase #3	$56.48	9.617%	$61.9117	$61.91	$61.90	$61.90
Purchase #4	$73.71	7.748%	$79.4211	$79.42	$79.40	$79.40
Purchase #5	$182.60	4.807%	$191.3776	$191.38	$191.40	$191.40
Purchase #6	$85.76	4.143%	$89.313	$89.31	$89.30	$89.30
Purchase #7	$54.58	13.762%	$62.0913	$62.09	$62.10	$62.10
7 purchase totals =	$627.83		$674.7734	$674.76	$674.75	$674.70