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	$61.32	10.603%	$67.8218	$67.82	$67.80	$67.80
Purchase #2	$56.96	3.861%	$59.1592	$59.16	$59.15	$59.20
Purchase #3	$179.55	8.174%	$194.2264	$194.23	$194.25	$194.20
Purchase #4	$153.62	11.540%	$171.3477	$171.35	$171.35	$171.30
Purchase #5	$113.72	13.573%	$129.1552	$129.16	$129.15	$129.20
Purchase #6	$168.59	13.469%	$191.2974	$191.30	$191.30	$191.30
Purchase #7	$116.73	3.526%	$120.8459	$120.85	$120.85	$120.80
7 purchase totals =	$850.49		$933.8536	$933.87	$933.85	$933.80