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	$82.47	8.222%	$89.2507	$89.25	$89.25	$89.30
Purchase #2	$49.25	6.561%	$52.4813	$52.48	$52.50	$52.50
Purchase #3	$44.29	3.719%	$45.9371	$45.94	$45.95	$45.90
Purchase #4	$101.58	4.793%	$106.4487	$106.45	$106.45	$106.40
Purchase #5	$188.97	11.331%	$210.3822	$210.38	$210.40	$210.40
Purchase #6	$120.82	6.822%	$129.0623	$129.06	$129.05	$129.10
Purchase #7	$47.88	8.401%	$51.9024	$51.90	$51.90	$51.90
7 purchase totals =	$635.26		$685.4647	$685.46	$685.50	$685.50