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	$62.44	5.474%	$65.858	$65.86	$65.85	$65.90
Purchase #2	$148.42	10.443%	$163.9195	$163.92	$163.90	$163.90
Purchase #3	$99.65	5.820%	$105.4496	$105.45	$105.45	$105.40
Purchase #4	$89.72	3.380%	$92.7525	$92.75	$92.75	$92.80
Purchase #5	$57.49	8.107%	$62.1507	$62.15	$62.15	$62.20
Purchase #6	$65.96	10.581%	$72.9392	$72.94	$72.95	$72.90
Purchase #7	$218.47	11.338%	$243.2401	$243.24	$243.25	$243.20
7 purchase totals =	$742.15		$806.3096	$806.31	$806.30	$806.30