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	$244.40	12.695%	$275.4266	$275.43	$275.45	$275.40
Purchase #2	$93.96	6.194%	$99.7799	$99.78	$99.80	$99.80
Purchase #3	$200.78	6.670%	$214.172	$214.17	$214.15	$214.20
Purchase #4	$44.33	7.249%	$47.5435	$47.54	$47.55	$47.50
Purchase #5	$84.79	4.117%	$88.2808	$88.28	$88.30	$88.30
Purchase #6	$152.88	10.752%	$169.3177	$169.32	$169.30	$169.30
Purchase #7	$123.44	4.470%	$128.9578	$128.96	$128.95	$129.00
7 purchase totals =	$944.58		$1,023.4783	$1,023.48	$1,023.50	$1,023.50