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	$247.91	7.543%	$266.6099	$266.61	$266.60	$266.60
Purchase #2	$180.98	9.225%	$197.6754	$197.68	$197.70	$197.70
Purchase #3	$43.35	11.798%	$48.4644	$48.46	$48.45	$48.50
Purchase #4	$145.49	4.785%	$152.4517	$152.45	$152.45	$152.50
Purchase #5	$161.89	3.814%	$168.0645	$168.06	$168.05	$168.10
Purchase #6	$204.33	9.336%	$223.4062	$223.41	$223.40	$223.40
Purchase #7	$123.60	3.290%	$127.6664	$127.67	$127.65	$127.70
7 purchase totals =	$1,107.55		$1,184.3385	$1,184.34	$1,184.30	$1,184.50