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	$90.31	8.670%	$98.1399	$98.14	$98.15	$98.10
Purchase #2	$105.53	6.106%	$111.9737	$111.97	$111.95	$112.00
Purchase #3	$181.46	13.601%	$206.1404	$206.14	$206.15	$206.10
Purchase #4	$167.81	7.825%	$180.9411	$180.94	$180.95	$180.90
Purchase #5	$37.50	13.172%	$42.4395	$42.44	$42.45	$42.40
Purchase #6	$22.34	8.206%	$24.1732	$24.17	$24.15	$24.20
Purchase #7	$42.74	6.156%	$45.3711	$45.37	$45.35	$45.40
7 purchase totals =	$647.69		$709.1789	$709.17	$709.15	$709.10