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	$144.88	4.521%	$151.43	$151.43	$151.45	$151.40
Purchase #2	$86.87	13.109%	$98.2578	$98.26	$98.25	$98.30
Purchase #3	$17.50	9.220%	$19.1135	$19.11	$19.10	$19.10
Purchase #4	$98.26	13.254%	$111.2834	$111.28	$111.30	$111.30
Purchase #5	$40.48	8.312%	$43.8447	$43.84	$43.85	$43.80
Purchase #6	$63.76	11.201%	$70.9018	$70.90	$70.90	$70.90
Purchase #7	$220.54	10.231%	$243.1034	$243.10	$243.10	$243.10
7 purchase totals =	$672.29		$737.9346	$737.92	$737.95	$737.90