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	$198.25	10.621%	$219.3061	$219.31	$219.30	$219.30
Purchase #2	$57.98	8.498%	$62.9071	$62.91	$62.90	$62.90
Purchase #3	$98.77	4.676%	$103.3885	$103.39	$103.40	$103.40
Purchase #4	$102.81	11.286%	$114.4131	$114.41	$114.40	$114.40
Purchase #5	$126.79	12.125%	$142.1633	$142.16	$142.15	$142.20
Purchase #6	$242.48	5.414%	$255.6079	$255.61	$255.60	$255.60
Purchase #7	$196.77	5.519%	$207.6297	$207.63	$207.65	$207.60
7 purchase totals =	$1,023.85		$1,105.4157	$1,105.42	$1,105.40	$1,105.40