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	$192.29	8.602%	$208.8308	$208.83	$208.85	$208.80
Purchase #2	$158.57	4.137%	$165.13	$165.13	$165.15	$165.10
Purchase #3	$147.69	5.735%	$156.16	$156.16	$156.15	$156.20
Purchase #4	$199.81	6.141%	$212.0803	$212.08	$212.10	$212.10
Purchase #5	$67.33	7.407%	$72.3171	$72.32	$72.30	$72.30
Purchase #6	$86.28	7.625%	$92.8589	$92.86	$92.85	$92.90
Purchase #7	$52.25	3.302%	$53.9753	$53.98	$54.00	$54.00
7 purchase totals =	$904.22		$961.3524	$961.36	$961.40	$961.40