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	$189.99	11.152%	$211.1777	$211.18	$211.20	$211.20
Purchase #2	$247.68	9.631%	$271.5341	$271.53	$271.55	$271.50
Purchase #3	$112.61	9.763%	$123.6041	$123.60	$123.60	$123.60
Purchase #4	$23.33	3.340%	$24.1092	$24.11	$24.10	$24.10
Purchase #5	$210.98	3.107%	$217.5351	$217.54	$217.55	$217.50
Purchase #6	$141.34	6.364%	$150.3349	$150.33	$150.35	$150.30
Purchase #7	$138.73	9.674%	$152.1507	$152.15	$152.15	$152.20
7 purchase totals =	$1,064.66		$1,150.4458	$1,150.44	$1,150.50	$1,150.40