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	$200.66	5.267%	$211.2288	$211.23	$211.25	$211.20
Purchase #2	$36.36	4.686%	$38.0638	$38.06	$38.05	$38.10
Purchase #3	$109.65	5.464%	$115.6413	$115.64	$115.65	$115.60
Purchase #4	$150.65	8.118%	$162.8798	$162.88	$162.90	$162.90
Purchase #5	$148.72	5.502%	$156.9026	$156.90	$156.90	$156.90
Purchase #6	$6.43	13.620%	$7.3058	$7.31	$7.30	$7.30
Purchase #7	$90.76	4.521%	$94.8633	$94.86	$94.85	$94.90
7 purchase totals =	$743.23		$786.8854	$786.88	$786.90	$786.90