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	$130.62	8.450%	$141.6574	$141.66	$141.65	$141.70
Purchase #2	$158.74	13.244%	$179.7635	$179.76	$179.75	$179.80
Purchase #3	$56.37	6.150%	$59.8368	$59.84	$59.85	$59.80
Purchase #4	$210.33	4.526%	$219.8495	$219.85	$219.85	$219.80
Purchase #5	$242.46	13.688%	$275.6479	$275.65	$275.65	$275.60
Purchase #6	$17.66	9.458%	$19.3303	$19.33	$19.35	$19.30
Purchase #7	$102.54	3.654%	$106.2868	$106.29	$106.30	$106.30
7 purchase totals =	$918.72		$1,002.3722	$1,002.38	$1,002.40	$1,002.30