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	$178.85	3.722%	$185.5068	$185.51	$185.50	$185.50
Purchase #2	$88.80	13.405%	$100.7036	$100.70	$100.70	$100.70
Purchase #3	$28.89	11.244%	$32.1384	$32.14	$32.15	$32.10
Purchase #4	$221.68	10.700%	$245.3998	$245.40	$245.40	$245.40
Purchase #5	$174.90	11.174%	$194.4433	$194.44	$194.45	$194.40
Purchase #6	$56.47	5.550%	$59.6041	$59.60	$59.60	$59.60
Purchase #7	$173.53	5.726%	$183.4663	$183.47	$183.45	$183.50
7 purchase totals =	$923.12		$1,001.2623	$1,001.26	$1,001.25	$1,001.20