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	$70.48	3.804%	$73.1611	$73.16	$73.15	$73.20
Purchase #2	$165.53	10.288%	$182.5597	$182.56	$182.55	$182.60
Purchase #3	$233.57	10.520%	$258.1416	$258.14	$258.15	$258.10
Purchase #4	$157.88	10.512%	$174.4763	$174.48	$174.50	$174.50
Purchase #5	$154.54	12.661%	$174.1063	$174.11	$174.10	$174.10
Purchase #6	$20.86	4.521%	$21.8031	$21.80	$21.80	$21.80
Purchase #7	$240.28	12.855%	$271.168	$271.17	$271.15	$271.20
7 purchase totals =	$1,043.14		$1,155.4161	$1,155.42	$1,155.40	$1,155.50