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	$168.32	10.183%	$185.46	$185.46	$185.45	$185.50
Purchase #2	$188.32	11.773%	$210.4909	$210.49	$210.50	$210.50
Purchase #3	$145.33	3.187%	$149.9617	$149.96	$149.95	$150.00
Purchase #4	$191.51	10.384%	$211.3964	$211.40	$211.40	$211.40
Purchase #5	$85.40	8.643%	$92.7811	$92.78	$92.80	$92.80
Purchase #6	$206.87	4.121%	$215.3951	$215.40	$215.40	$215.40
Purchase #7	$16.89	5.695%	$17.8519	$17.85	$17.85	$17.90
7 purchase totals =	$1,002.64		$1,083.3371	$1,083.34	$1,083.35	$1,083.50