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	$167.79	10.790%	$185.8945	$185.89	$185.90	$185.90
Purchase #2	$17.48	6.143%	$18.5538	$18.55	$18.55	$18.60
Purchase #3	$125.28	12.374%	$140.7821	$140.78	$140.80	$140.80
Purchase #4	$175.56	11.838%	$196.3428	$196.34	$196.35	$196.30
Purchase #5	$176.65	10.141%	$194.5641	$194.56	$194.55	$194.60
Purchase #6	$118.32	10.454%	$130.6892	$130.69	$130.70	$130.70
Purchase #7	$192.93	6.854%	$206.1534	$206.15	$206.15	$206.20
7 purchase totals =	$974.01		$1,072.9799	$1,072.96	$1,073.00	$1,073.10