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	$209.76	13.484%	$238.044	$238.04	$238.05	$238.00
Purchase #2	$194.34	9.157%	$212.1357	$212.14	$212.15	$212.10
Purchase #3	$93.73	5.104%	$98.514	$98.51	$98.50	$98.50
Purchase #4	$178.74	10.788%	$198.0225	$198.02	$198.00	$198.00
Purchase #5	$48.87	3.514%	$50.5873	$50.59	$50.60	$50.60
Purchase #6	$42.67	9.774%	$46.8406	$46.84	$46.85	$46.80
Purchase #7	$100.50	3.616%	$104.1341	$104.13	$104.15	$104.10
7 purchase totals =	$868.61		$948.2782	$948.27	$948.30	$948.10