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	$28.94	6.223%	$30.7409	$30.74	$30.75	$30.70
Purchase #2	$112.72	13.358%	$127.7771	$127.78	$127.80	$127.80
Purchase #3	$181.56	9.855%	$199.4527	$199.45	$199.45	$199.50
Purchase #4	$166.75	3.354%	$172.3428	$172.34	$172.35	$172.30
Purchase #5	$209.79	5.313%	$220.9361	$220.94	$220.95	$220.90
Purchase #6	$199.93	3.714%	$207.3554	$207.36	$207.35	$207.40
Purchase #7	$139.51	9.328%	$152.5235	$152.52	$152.50	$152.50
7 purchase totals =	$1,039.20		$1,111.1285	$1,111.13	$1,111.15	$1,111.10