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	$149.99	12.128%	$168.1808	$168.18	$168.20	$168.20
Purchase #2	$6.89	8.781%	$7.495	$7.50	$7.50	$7.50
Purchase #3	$148.60	13.262%	$168.3073	$168.31	$168.30	$168.30
Purchase #4	$91.76	9.434%	$100.4166	$100.42	$100.40	$100.40
Purchase #5	$173.96	7.290%	$186.6417	$186.64	$186.65	$186.60
Purchase #6	$206.56	7.423%	$221.8929	$221.89	$221.90	$221.90
Purchase #7	$93.70	6.844%	$100.1128	$100.11	$100.10	$100.10
7 purchase totals =	$871.46		$953.0471	$953.05	$953.05	$953.00