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	$237.86	13.220%	$269.3051	$269.31	$269.30	$269.30
Purchase #2	$86.76	13.655%	$98.6071	$98.61	$98.60	$98.60
Purchase #3	$94.28	6.566%	$100.4704	$100.47	$100.45	$100.50
Purchase #4	$229.50	6.753%	$244.9981	$245.00	$245.00	$245.00
Purchase #5	$73.37	8.633%	$79.704	$79.70	$79.70	$79.70
Purchase #6	$238.70	10.718%	$264.2839	$264.28	$264.30	$264.30
Purchase #7	$124.36	12.147%	$139.466	$139.47	$139.45	$139.50
7 purchase totals =	$1,084.83		$1,196.8346	$1,196.84	$1,196.80	$1,196.90