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	$57.63	6.651%	$61.463	$61.46	$61.45	$61.50
Purchase #2	$56.46	13.309%	$63.9743	$63.97	$63.95	$64.00
Purchase #3	$78.34	13.798%	$89.1494	$89.15	$89.15	$89.10
Purchase #4	$104.69	4.162%	$109.0472	$109.05	$109.05	$109.00
Purchase #5	$166.46	13.662%	$189.2018	$189.20	$189.20	$189.20
Purchase #6	$94.40	7.234%	$101.2289	$101.23	$101.25	$101.20
Purchase #7	$197.30	13.476%	$223.8881	$223.89	$223.90	$223.90
7 purchase totals =	$755.28		$837.9527	$837.95	$837.95	$837.90