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	$67.90	7.544%	$73.0224	$73.02	$73.00	$73.00
Purchase #2	$195.69	8.108%	$211.5565	$211.56	$211.55	$211.60
Purchase #3	$39.88	6.769%	$42.5795	$42.58	$42.60	$42.60
Purchase #4	$193.91	6.476%	$206.4676	$206.47	$206.45	$206.50
Purchase #5	$104.71	13.799%	$119.1589	$119.16	$119.15	$119.20
Purchase #6	$65.57	11.206%	$72.9178	$72.92	$72.90	$72.90
Purchase #7	$111.93	6.662%	$119.3868	$119.39	$119.40	$119.40
7 purchase totals =	$779.59		$845.0895	$845.10	$845.05	$845.20