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	$53.33	12.226%	$59.8501	$59.85	$59.85	$59.90
Purchase #2	$115.36	10.667%	$127.6655	$127.67	$127.65	$127.70
Purchase #3	$83.43	11.132%	$92.7174	$92.72	$92.70	$92.70
Purchase #4	$233.77	9.625%	$256.2704	$256.27	$256.25	$256.30
Purchase #5	$53.80	5.210%	$56.603	$56.60	$56.60	$56.60
Purchase #6	$100.98	11.283%	$112.3736	$112.37	$112.35	$112.40
Purchase #7	$89.68	9.728%	$98.4041	$98.40	$98.40	$98.40
7 purchase totals =	$730.35		$803.8841	$803.88	$803.80	$804.00