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	$207.75	5.776%	$219.7496	$219.75	$219.75	$219.70
Purchase #2	$157.93	11.270%	$175.7287	$175.73	$175.75	$175.70
Purchase #3	$161.58	4.121%	$168.2387	$168.24	$168.25	$168.20
Purchase #4	$145.86	4.244%	$152.0503	$152.05	$152.05	$152.10
Purchase #5	$61.35	5.341%	$64.6267	$64.63	$64.65	$64.60
Purchase #6	$82.41	8.806%	$89.667	$89.67	$89.65	$89.70
Purchase #7	$19.52	3.838%	$20.2692	$20.27	$20.25	$20.30
7 purchase totals =	$836.40		$890.3302	$890.34	$890.35	$890.30