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	$99.33	7.504%	$106.7837	$106.78	$106.80	$106.80
Purchase #2	$54.96	11.608%	$61.3398	$61.34	$61.35	$61.30
Purchase #3	$87.85	7.535%	$94.4695	$94.47	$94.45	$94.50
Purchase #4	$152.55	10.497%	$168.5632	$168.56	$168.55	$168.60
Purchase #5	$9.91	5.812%	$10.486	$10.49	$10.50	$10.50
Purchase #6	$181.90	10.207%	$200.4665	$200.47	$200.45	$200.50
Purchase #7	$230.76	6.324%	$245.3533	$245.35	$245.35	$245.40
7 purchase totals =	$817.26		$887.4620	$887.46	$887.45	$887.60