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	$240.84	10.376%	$265.8296	$265.83	$265.85	$265.80
Purchase #2	$243.79	12.179%	$273.4812	$273.48	$273.50	$273.50
Purchase #3	$38.44	9.568%	$42.1179	$42.12	$42.10	$42.10
Purchase #4	$78.67	8.394%	$85.2736	$85.27	$85.25	$85.30
Purchase #5	$244.44	13.450%	$277.3172	$277.32	$277.30	$277.30
Purchase #6	$77.78	6.494%	$82.831	$82.83	$82.85	$82.80
Purchase #7	$8.25	7.534%	$8.8716	$8.87	$8.85	$8.90
7 purchase totals =	$932.21		$1,035.7221	$1,035.72	$1,035.70	$1,035.70