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	$200.82	10.744%	$222.3961	$222.40	$222.40	$222.40
Purchase #2	$23.84	9.795%	$26.1751	$26.18	$26.20	$26.20
Purchase #3	$168.48	7.158%	$180.5398	$180.54	$180.55	$180.50
Purchase #4	$119.61	6.185%	$127.0079	$127.01	$127.00	$127.00
Purchase #5	$136.77	10.130%	$150.6248	$150.62	$150.60	$150.60
Purchase #6	$172.41	9.543%	$188.8631	$188.86	$188.85	$188.90
Purchase #7	$191.36	9.373%	$209.2962	$209.30	$209.30	$209.30
7 purchase totals =	$1,013.29		$1,104.9030	$1,104.91	$1,104.90	$1,104.90