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	$172.86	5.558%	$182.4676	$182.47	$182.45	$182.50
Purchase #2	$142.81	10.741%	$158.1492	$158.15	$158.15	$158.10
Purchase #3	$92.35	4.363%	$96.3792	$96.38	$96.40	$96.40
Purchase #4	$230.60	10.661%	$255.1843	$255.18	$255.20	$255.20
Purchase #5	$80.44	10.567%	$88.9401	$88.94	$88.95	$88.90
Purchase #6	$182.39	7.400%	$195.8869	$195.89	$195.90	$195.90
Purchase #7	$51.72	4.310%	$53.9491	$53.95	$53.95	$53.90
7 purchase totals =	$953.17		$1,030.9564	$1,030.96	$1,031.00	$1,030.90