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	$92.46	6.154%	$98.15	$98.15	$98.15	$98.20
Purchase #2	$102.80	8.110%	$111.1371	$111.14	$111.15	$111.10
Purchase #3	$61.73	4.716%	$64.6412	$64.64	$64.65	$64.60
Purchase #4	$60.48	9.678%	$66.3333	$66.33	$66.35	$66.30
Purchase #5	$94.92	11.745%	$106.0684	$106.07	$106.05	$106.10
Purchase #6	$20.26	9.294%	$22.143	$22.14	$22.15	$22.10
Purchase #7	$61.73	13.474%	$70.0475	$70.05	$70.05	$70.00
7 purchase totals =	$494.38		$538.5205	$538.52	$538.55	$538.40