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	$219.72	5.206%	$231.1586	$231.16	$231.15	$231.20
Purchase #2	$179.46	3.611%	$185.9403	$185.94	$185.95	$185.90
Purchase #3	$207.36	10.745%	$229.6408	$229.64	$229.65	$229.60
Purchase #4	$159.78	6.768%	$170.5939	$170.59	$170.60	$170.60
Purchase #5	$219.40	8.696%	$238.479	$238.48	$238.50	$238.50
Purchase #6	$98.56	6.332%	$104.8008	$104.80	$104.80	$104.80
Purchase #7	$72.62	12.375%	$81.6067	$81.61	$81.60	$81.60
7 purchase totals =	$1,156.90		$1,242.2201	$1,242.22	$1,242.25	$1,242.20