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	$45.34	7.518%	$48.7487	$48.75	$48.75	$48.70
Purchase #2	$167.74	7.401%	$180.1544	$180.15	$180.15	$180.20
Purchase #3	$41.29	10.405%	$45.5862	$45.59	$45.60	$45.60
Purchase #4	$64.56	11.557%	$72.0212	$72.02	$72.00	$72.00
Purchase #5	$203.33	12.802%	$229.3603	$229.36	$229.35	$229.40
Purchase #6	$104.93	4.192%	$109.3287	$109.33	$109.35	$109.30
Purchase #7	$248.66	3.789%	$258.0817	$258.08	$258.10	$258.10
7 purchase totals =	$875.85		$943.2812	$943.28	$943.30	$943.30