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	$182.95	5.233%	$192.5238	$192.52	$192.50	$192.50
Purchase #2	$73.75	11.825%	$82.4709	$82.47	$82.45	$82.50
Purchase #3	$133.28	13.745%	$151.5993	$151.60	$151.60	$151.60
Purchase #4	$98.64	7.353%	$105.893	$105.89	$105.90	$105.90
Purchase #5	$188.98	3.422%	$195.4469	$195.45	$195.45	$195.40
Purchase #6	$35.41	4.861%	$37.1313	$37.13	$37.15	$37.10
Purchase #7	$198.37	7.539%	$213.3251	$213.33	$213.35	$213.30
7 purchase totals =	$911.38		$978.3903	$978.39	$978.40	$978.30