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	$101.85	3.199%	$105.1082	$105.11	$105.10	$105.10
Purchase #2	$215.33	5.529%	$227.2356	$227.24	$227.25	$227.20
Purchase #3	$70.87	12.263%	$79.5608	$79.56	$79.55	$79.60
Purchase #4	$136.53	10.113%	$150.3373	$150.34	$150.35	$150.30
Purchase #5	$159.73	4.458%	$166.8508	$166.85	$166.85	$166.90
Purchase #6	$160.46	11.589%	$179.0557	$179.06	$179.05	$179.10
Purchase #7	$197.60	8.858%	$215.1034	$215.10	$215.10	$215.10
7 purchase totals =	$1,042.37		$1,123.2518	$1,123.26	$1,123.25	$1,123.30