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	$160.63	6.150%	$170.5087	$170.51	$170.50	$170.50
Purchase #2	$159.61	3.658%	$165.4485	$165.45	$165.45	$165.40
Purchase #3	$73.56	13.666%	$83.6127	$83.61	$83.60	$83.60
Purchase #4	$187.86	11.418%	$209.3099	$209.31	$209.30	$209.30
Purchase #5	$86.43	6.234%	$91.818	$91.82	$91.80	$91.80
Purchase #6	$246.98	10.695%	$273.3945	$273.39	$273.40	$273.40
Purchase #7	$35.82	12.857%	$40.4254	$40.43	$40.45	$40.40
7 purchase totals =	$950.89		$1,034.5177	$1,034.52	$1,034.50	$1,034.40