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	$34.83	6.644%	$37.1441	$37.14	$37.15	$37.10
Purchase #2	$105.89	3.116%	$109.1895	$109.19	$109.20	$109.20
Purchase #3	$168.27	13.367%	$190.7627	$190.76	$190.75	$190.80
Purchase #4	$90.45	7.404%	$97.1469	$97.15	$97.15	$97.10
Purchase #5	$42.85	7.590%	$46.1023	$46.10	$46.10	$46.10
Purchase #6	$188.65	7.524%	$202.844	$202.84	$202.85	$202.80
Purchase #7	$239.59	10.547%	$264.8596	$264.86	$264.85	$264.90
7 purchase totals =	$870.53		$948.0491	$948.04	$948.05	$948.00