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	$97.91	11.333%	$109.0061	$109.01	$109.00	$109.00
Purchase #2	$12.73	4.550%	$13.3092	$13.31	$13.30	$13.30
Purchase #3	$145.72	12.594%	$164.072	$164.07	$164.05	$164.10
Purchase #4	$196.55	11.740%	$219.625	$219.63	$219.65	$219.60
Purchase #5	$161.81	11.422%	$180.2919	$180.29	$180.30	$180.30
Purchase #6	$81.74	13.251%	$92.5714	$92.57	$92.55	$92.60
Purchase #7	$129.77	3.471%	$134.2743	$134.27	$134.25	$134.30
7 purchase totals =	$826.23		$913.1499	$913.15	$913.10	$913.20