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	$173.96	9.774%	$190.9629	$190.96	$190.95	$191.00
Purchase #2	$24.52	13.573%	$27.8481	$27.85	$27.85	$27.80
Purchase #3	$55.42	11.195%	$61.6243	$61.62	$61.60	$61.60
Purchase #4	$88.36	11.267%	$98.3155	$98.32	$98.30	$98.30
Purchase #5	$240.41	10.623%	$265.9488	$265.95	$265.95	$265.90
Purchase #6	$94.40	6.617%	$100.6464	$100.65	$100.65	$100.60
Purchase #7	$176.99	5.235%	$186.2554	$186.26	$186.25	$186.30
7 purchase totals =	$854.06		$931.6014	$931.61	$931.55	$931.50