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	$130.74	13.214%	$148.016	$148.02	$148.00	$148.00
Purchase #2	$135.84	10.863%	$150.5963	$150.60	$150.60	$150.60
Purchase #3	$171.28	4.158%	$178.4018	$178.40	$178.40	$178.40
Purchase #4	$236.76	11.664%	$264.3757	$264.38	$264.40	$264.40
Purchase #5	$229.60	4.774%	$240.5611	$240.56	$240.55	$240.60
Purchase #6	$29.34	13.776%	$33.3819	$33.38	$33.40	$33.40
Purchase #7	$97.29	5.122%	$102.2732	$102.27	$102.25	$102.30
7 purchase totals =	$1,030.85		$1,117.6060	$1,117.61	$1,117.60	$1,117.70