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	$197.82	5.673%	$209.0423	$209.04	$209.05	$209.00
Purchase #2	$240.58	13.598%	$273.2941	$273.29	$273.30	$273.30
Purchase #3	$134.57	6.286%	$143.0291	$143.03	$143.05	$143.00
Purchase #4	$123.53	10.722%	$136.7749	$136.77	$136.75	$136.80
Purchase #5	$193.67	11.216%	$215.392	$215.39	$215.40	$215.40
Purchase #6	$85.99	4.404%	$89.777	$89.78	$89.80	$89.80
Purchase #7	$33.73	6.194%	$35.8192	$35.82	$35.80	$35.80
7 purchase totals =	$1,009.89		$1,103.1286	$1,103.12	$1,103.15	$1,103.10