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	$140.87	5.448%	$148.5446	$148.54	$148.55	$148.50
Purchase #2	$161.57	7.134%	$173.0964	$173.10	$173.10	$173.10
Purchase #3	$120.85	12.672%	$136.1641	$136.16	$136.15	$136.20
Purchase #4	$141.38	6.696%	$150.8468	$150.85	$150.85	$150.80
Purchase #5	$91.70	7.423%	$98.5069	$98.51	$98.50	$98.50
Purchase #6	$79.96	7.478%	$85.9394	$85.94	$85.95	$85.90
Purchase #7	$189.66	10.269%	$209.1362	$209.14	$209.15	$209.10
7 purchase totals =	$925.99		$1,002.2344	$1,002.24	$1,002.25	$1,002.10