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	$222.82	8.815%	$242.4616	$242.46	$242.45	$242.50
Purchase #2	$101.26	7.793%	$109.1512	$109.15	$109.15	$109.20
Purchase #3	$147.68	5.526%	$155.8408	$155.84	$155.85	$155.80
Purchase #4	$64.98	10.611%	$71.875	$71.88	$71.90	$71.90
Purchase #5	$210.51	4.382%	$219.7345	$219.73	$219.75	$219.70
Purchase #6	$229.82	8.144%	$248.5365	$248.54	$248.55	$248.50
Purchase #7	$143.85	6.149%	$152.6953	$152.70	$152.70	$152.70
7 purchase totals =	$1,120.92		$1,200.2949	$1,200.30	$1,200.35	$1,200.30