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	$99.41	6.673%	$106.0436	$106.04	$106.05	$106.00
Purchase #2	$229.69	8.872%	$250.0681	$250.07	$250.05	$250.10
Purchase #3	$93.87	5.607%	$99.1333	$99.13	$99.15	$99.10
Purchase #4	$129.38	3.679%	$134.1399	$134.14	$134.15	$134.10
Purchase #5	$155.66	4.164%	$162.1417	$162.14	$162.15	$162.10
Purchase #6	$134.33	6.160%	$142.6047	$142.60	$142.60	$142.60
Purchase #7	$158.25	5.592%	$167.0993	$167.10	$167.10	$167.10
7 purchase totals =	$1,000.59		$1,061.2306	$1,061.22	$1,061.25	$1,061.10