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	$87.76	10.724%	$97.1714	$97.17	$97.15	$97.20
Purchase #2	$18.82	9.123%	$20.5369	$20.54	$20.55	$20.50
Purchase #3	$83.48	10.564%	$92.2988	$92.30	$92.30	$92.30
Purchase #4	$94.42	10.738%	$104.5588	$104.56	$104.55	$104.60
Purchase #5	$87.39	5.154%	$91.8941	$91.89	$91.90	$91.90
Purchase #6	$210.31	9.555%	$230.4051	$230.41	$230.40	$230.40
Purchase #7	$123.97	4.569%	$129.6342	$129.63	$129.65	$129.60
7 purchase totals =	$706.15		$766.4993	$766.50	$766.50	$766.50