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	$186.29	5.454%	$196.4503	$196.45	$196.45	$196.50
Purchase #2	$234.97	9.279%	$256.7729	$256.77	$256.75	$256.80
Purchase #3	$166.26	8.120%	$179.7603	$179.76	$179.75	$179.80
Purchase #4	$60.28	7.234%	$64.6407	$64.64	$64.65	$64.60
Purchase #5	$104.78	4.848%	$109.8597	$109.86	$109.85	$109.90
Purchase #6	$140.85	6.619%	$150.1729	$150.17	$150.15	$150.20
Purchase #7	$197.62	7.159%	$211.7676	$211.77	$211.75	$211.80
7 purchase totals =	$1,091.05		$1,169.4244	$1,169.42	$1,169.35	$1,169.60