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	$67.28	6.764%	$71.8308	$71.83	$71.85	$71.80
Purchase #2	$21.32	12.795%	$24.0479	$24.05	$24.05	$24.00
Purchase #3	$159.94	12.223%	$179.4895	$179.49	$179.50	$179.50
Purchase #4	$19.70	4.407%	$20.5682	$20.57	$20.55	$20.60
Purchase #5	$130.42	9.442%	$142.7343	$142.73	$142.75	$142.70
Purchase #6	$167.63	10.562%	$185.3351	$185.34	$185.35	$185.30
Purchase #7	$203.92	3.550%	$211.1592	$211.16	$211.15	$211.20
7 purchase totals =	$770.21		$835.1650	$835.17	$835.20	$835.10