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	$222.65	8.719%	$242.0629	$242.06	$242.05	$242.10
Purchase #2	$174.56	11.150%	$194.0234	$194.02	$194.00	$194.00
Purchase #3	$37.76	4.565%	$39.4837	$39.48	$39.50	$39.50
Purchase #4	$155.30	10.253%	$171.2229	$171.22	$171.20	$171.20
Purchase #5	$35.82	10.450%	$39.5632	$39.56	$39.55	$39.60
Purchase #6	$42.85	6.516%	$45.6421	$45.64	$45.65	$45.60
Purchase #7	$108.51	11.816%	$121.3315	$121.33	$121.35	$121.30
7 purchase totals =	$777.45		$853.3297	$853.31	$853.30	$853.30