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	$182.74	4.502%	$190.967	$190.97	$190.95	$191.00
Purchase #2	$249.30	9.632%	$273.3126	$273.31	$273.30	$273.30
Purchase #3	$192.37	5.196%	$202.3655	$202.37	$202.35	$202.40
Purchase #4	$172.64	13.771%	$196.4143	$196.41	$196.40	$196.40
Purchase #5	$31.93	4.207%	$33.2733	$33.27	$33.25	$33.30
Purchase #6	$35.89	7.785%	$38.684	$38.68	$38.70	$38.70
Purchase #7	$203.90	7.630%	$219.4576	$219.46	$219.45	$219.50
7 purchase totals =	$1,068.77		$1,154.4743	$1,154.47	$1,154.40	$1,154.60