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	$80.78	13.428%	$91.6271	$91.63	$91.65	$91.60
Purchase #2	$29.51	10.437%	$32.59	$32.59	$32.60	$32.60
Purchase #3	$36.60	5.558%	$38.6342	$38.63	$38.65	$38.60
Purchase #4	$191.51	4.755%	$200.6163	$200.62	$200.60	$200.60
Purchase #5	$47.97	4.498%	$50.1277	$50.13	$50.15	$50.10
Purchase #6	$191.65	4.436%	$200.1516	$200.15	$200.15	$200.20
Purchase #7	$150.30	11.363%	$167.3786	$167.38	$167.40	$167.40
7 purchase totals =	$728.32		$781.1255	$781.13	$781.20	$781.10