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	$86.39	7.153%	$92.5695	$92.57	$92.55	$92.60
Purchase #2	$57.97	13.137%	$65.5855	$65.59	$65.60	$65.60
Purchase #3	$172.58	3.320%	$178.3097	$178.31	$178.30	$178.30
Purchase #4	$86.78	12.327%	$97.4774	$97.48	$97.50	$97.50
Purchase #5	$219.40	11.341%	$244.2822	$244.28	$244.30	$244.30
Purchase #6	$99.97	4.458%	$104.4267	$104.43	$104.45	$104.40
Purchase #7	$189.74	4.777%	$198.8039	$198.80	$198.80	$198.80
7 purchase totals =	$912.83		$981.4549	$981.46	$981.50	$981.50