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	$177.74	11.692%	$198.5214	$198.52	$198.50	$198.50
Purchase #2	$10.75	13.303%	$12.1801	$12.18	$12.20	$12.20
Purchase #3	$89.94	11.275%	$100.0807	$100.08	$100.10	$100.10
Purchase #4	$37.85	4.291%	$39.4741	$39.47	$39.45	$39.50
Purchase #5	$245.36	7.715%	$264.2895	$264.29	$264.30	$264.30
Purchase #6	$184.67	10.658%	$204.3521	$204.35	$204.35	$204.40
Purchase #7	$235.85	13.132%	$266.8218	$266.82	$266.80	$266.80
7 purchase totals =	$982.16		$1,085.7197	$1,085.71	$1,085.70	$1,085.80