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	$180.42	6.372%	$191.9164	$191.92	$191.90	$191.90
Purchase #2	$67.50	5.601%	$71.2807	$71.28	$71.30	$71.30
Purchase #3	$174.53	4.694%	$182.7224	$182.72	$182.70	$182.70
Purchase #4	$80.70	6.279%	$85.7672	$85.77	$85.75	$85.80
Purchase #5	$139.75	7.668%	$150.466	$150.47	$150.45	$150.50
Purchase #6	$193.82	7.296%	$207.9611	$207.96	$207.95	$208.00
Purchase #7	$223.64	13.581%	$254.0125	$254.01	$254.00	$254.00
7 purchase totals =	$1,060.36		$1,144.1263	$1,144.13	$1,144.05	$1,144.20