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	$191.98	6.706%	$204.8542	$204.85	$204.85	$204.90
Purchase #2	$112.91	12.795%	$127.3568	$127.36	$127.35	$127.40
Purchase #3	$146.73	8.473%	$159.1624	$159.16	$159.15	$159.20
Purchase #4	$179.98	10.825%	$199.4628	$199.46	$199.45	$199.50
Purchase #5	$145.35	9.779%	$159.5638	$159.56	$159.55	$159.60
Purchase #6	$101.67	7.677%	$109.4752	$109.48	$109.50	$109.50
Purchase #7	$130.96	7.221%	$140.4166	$140.42	$140.40	$140.40
7 purchase totals =	$1,009.58		$1,100.2918	$1,100.29	$1,100.25	$1,100.50