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	$120.58	4.539%	$126.0531	$126.05	$126.05	$126.10
Purchase #2	$53.28	7.523%	$57.2883	$57.29	$57.30	$57.30
Purchase #3	$90.71	6.118%	$96.2596	$96.26	$96.25	$96.30
Purchase #4	$147.82	13.312%	$167.4978	$167.50	$167.50	$167.50
Purchase #5	$25.44	12.307%	$28.5709	$28.57	$28.55	$28.60
Purchase #6	$39.68	7.338%	$42.5917	$42.59	$42.60	$42.60
Purchase #7	$180.73	3.499%	$187.0537	$187.05	$187.05	$187.10
7 purchase totals =	$658.24		$705.3151	$705.31	$705.30	$705.50