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	$76.66	3.631%	$79.4435	$79.44	$79.45	$79.40
Purchase #2	$64.89	9.335%	$70.9475	$70.95	$70.95	$70.90
Purchase #3	$95.95	3.425%	$99.2363	$99.24	$99.25	$99.20
Purchase #4	$165.51	5.271%	$174.234	$174.23	$174.25	$174.20
Purchase #5	$72.43	7.215%	$77.6558	$77.66	$77.65	$77.70
Purchase #6	$59.80	11.817%	$66.8666	$66.87	$66.85	$66.90
Purchase #7	$246.68	3.446%	$255.1806	$255.18	$255.20	$255.20
7 purchase totals =	$781.92		$823.5643	$823.57	$823.60	$823.50