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	$211.87	4.541%	$221.491	$221.49	$221.50	$221.50
Purchase #2	$96.62	7.342%	$103.7138	$103.71	$103.70	$103.70
Purchase #3	$87.37	4.739%	$91.5105	$91.51	$91.50	$91.50
Purchase #4	$209.60	3.288%	$216.4916	$216.49	$216.50	$216.50
Purchase #5	$208.85	9.830%	$229.38	$229.38	$229.40	$229.40
Purchase #6	$221.61	3.132%	$228.5508	$228.55	$228.55	$228.60
Purchase #7	$56.88	3.578%	$58.9152	$58.92	$58.90	$58.90
7 purchase totals =	$1,092.80		$1,150.0529	$1,150.05	$1,150.05	$1,150.10