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	$148.46	12.146%	$166.492	$166.49	$166.50	$166.50
Purchase #2	$79.72	3.274%	$82.33	$82.33	$82.35	$82.30
Purchase #3	$63.46	6.428%	$67.5392	$67.54	$67.55	$67.50
Purchase #4	$53.69	12.398%	$60.3465	$60.35	$60.35	$60.30
Purchase #5	$51.79	8.634%	$56.2615	$56.26	$56.25	$56.30
Purchase #6	$236.57	12.131%	$265.2683	$265.27	$265.25	$265.30
Purchase #7	$43.76	9.159%	$47.768	$47.77	$47.75	$47.80
7 purchase totals =	$677.45		$746.0055	$746.01	$746.00	$746.00