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	$132.48	7.453%	$142.3537	$142.35	$142.35	$142.40
Purchase #2	$92.78	10.229%	$102.2705	$102.27	$102.25	$102.30
Purchase #3	$233.98	11.331%	$260.4923	$260.49	$260.50	$260.50
Purchase #4	$229.77	11.199%	$255.5019	$255.50	$255.50	$255.50
Purchase #5	$130.47	6.440%	$138.8723	$138.87	$138.85	$138.90
Purchase #6	$10.34	7.642%	$11.1302	$11.13	$11.15	$11.10
Purchase #7	$132.35	9.650%	$145.1218	$145.12	$145.10	$145.10
7 purchase totals =	$962.17		$1,055.7427	$1,055.73	$1,055.70	$1,055.80