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	$151.90	3.445%	$157.133	$157.13	$157.15	$157.10
Purchase #2	$188.31	13.339%	$213.4287	$213.43	$213.45	$213.40
Purchase #3	$95.98	8.274%	$103.9214	$103.92	$103.90	$103.90
Purchase #4	$92.36	7.428%	$99.2205	$99.22	$99.20	$99.20
Purchase #5	$62.80	10.370%	$69.3124	$69.31	$69.30	$69.30
Purchase #6	$233.84	8.355%	$253.3773	$253.38	$253.40	$253.40
Purchase #7	$144.57	3.805%	$150.0709	$150.07	$150.05	$150.10
7 purchase totals =	$969.76		$1,046.4642	$1,046.46	$1,046.45	$1,046.40