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	$86.97	3.492%	$90.007	$90.01	$90.00	$90.00
Purchase #2	$85.35	11.753%	$95.3812	$95.38	$95.40	$95.40
Purchase #3	$235.66	4.355%	$245.923	$245.92	$245.90	$245.90
Purchase #4	$95.81	10.323%	$105.7005	$105.70	$105.70	$105.70
Purchase #5	$168.74	5.391%	$177.8368	$177.84	$177.85	$177.80
Purchase #6	$211.27	5.288%	$222.442	$222.44	$222.45	$222.40
Purchase #7	$112.32	10.655%	$124.2877	$124.29	$124.30	$124.30
7 purchase totals =	$996.12		$1,061.5782	$1,061.58	$1,061.60	$1,061.50