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	$246.56	7.293%	$264.5416	$264.54	$264.55	$264.50
Purchase #2	$123.84	12.790%	$139.6791	$139.68	$139.70	$139.70
Purchase #3	$101.44	13.279%	$114.9102	$114.91	$114.90	$114.90
Purchase #4	$240.57	6.704%	$256.6978	$256.70	$256.70	$256.70
Purchase #5	$85.33	6.478%	$90.8577	$90.86	$90.85	$90.90
Purchase #6	$122.46	6.425%	$130.3281	$130.33	$130.35	$130.30
Purchase #7	$17.66	10.542%	$19.5217	$19.52	$19.50	$19.50
7 purchase totals =	$937.86		$1,016.5362	$1,016.54	$1,016.55	$1,016.50