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	$218.89	4.685%	$229.145	$229.15	$229.15	$229.10
Purchase #2	$129.39	3.844%	$134.3638	$134.36	$134.35	$134.40
Purchase #3	$54.25	12.515%	$61.0394	$61.04	$61.05	$61.00
Purchase #4	$227.53	4.504%	$237.778	$237.78	$237.80	$237.80
Purchase #5	$149.27	12.729%	$168.2706	$168.27	$168.25	$168.30
Purchase #6	$133.61	5.270%	$140.6512	$140.65	$140.65	$140.70
Purchase #7	$124.71	12.574%	$140.391	$140.39	$140.40	$140.40
7 purchase totals =	$1,037.65		$1,111.6390	$1,111.64	$1,111.65	$1,111.70