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	$59.34	4.220%	$61.8441	$61.84	$61.85	$61.80
Purchase #2	$89.63	11.170%	$99.6417	$99.64	$99.65	$99.60
Purchase #3	$41.56	9.203%	$45.3848	$45.38	$45.40	$45.40
Purchase #4	$122.82	13.309%	$139.1661	$139.17	$139.15	$139.20
Purchase #5	$175.59	4.732%	$183.8989	$183.90	$183.90	$183.90
Purchase #6	$108.62	9.518%	$118.9585	$118.96	$118.95	$119.00
Purchase #7	$30.44	6.292%	$32.3553	$32.36	$32.35	$32.40
7 purchase totals =	$628.00		$681.2494	$681.25	$681.25	$681.30