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	$99.47	9.707%	$109.1256	$109.13	$109.15	$109.10
Purchase #2	$88.30	4.496%	$92.27	$92.27	$92.25	$92.30
Purchase #3	$67.94	7.635%	$73.1272	$73.13	$73.15	$73.10
Purchase #4	$100.93	9.111%	$110.1257	$110.13	$110.15	$110.10
Purchase #5	$50.40	5.168%	$53.0047	$53.00	$53.00	$53.00
Purchase #6	$114.97	10.632%	$127.1936	$127.19	$127.20	$127.20
Purchase #7	$140.75	5.470%	$148.449	$148.45	$148.45	$148.40
7 purchase totals =	$662.76		$713.2958	$713.30	$713.35	$713.20