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	$168.35	11.331%	$187.4257	$187.43	$187.45	$187.40
Purchase #2	$85.79	7.673%	$92.3727	$92.37	$92.35	$92.40
Purchase #3	$222.88	4.615%	$233.1659	$233.17	$233.15	$233.20
Purchase #4	$71.27	12.221%	$79.9799	$79.98	$80.00	$80.00
Purchase #5	$109.33	13.736%	$124.3476	$124.35	$124.35	$124.30
Purchase #6	$40.39	4.177%	$42.0771	$42.08	$42.10	$42.10
Purchase #7	$30.89	10.178%	$34.034	$34.03	$34.05	$34.00
7 purchase totals =	$728.90		$793.4029	$793.41	$793.45	$793.40