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	$49.33	11.366%	$54.9368	$54.94	$54.95	$54.90
Purchase #2	$75.39	9.534%	$82.5777	$82.58	$82.60	$82.60
Purchase #3	$211.38	6.783%	$225.7179	$225.72	$225.70	$225.70
Purchase #4	$246.54	9.201%	$269.2241	$269.22	$269.20	$269.20
Purchase #5	$96.98	3.568%	$100.4402	$100.44	$100.45	$100.40
Purchase #6	$249.28	13.201%	$282.1875	$282.19	$282.20	$282.20
Purchase #7	$31.88	10.294%	$35.1617	$35.16	$35.15	$35.20
7 purchase totals =	$960.78		$1,050.2459	$1,050.25	$1,050.25	$1,050.20