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	$180.88	8.449%	$196.1626	$196.16	$196.15	$196.20
Purchase #2	$182.37	4.283%	$190.1809	$190.18	$190.20	$190.20
Purchase #3	$149.84	12.692%	$168.8577	$168.86	$168.85	$168.90
Purchase #4	$96.86	9.374%	$105.9397	$105.94	$105.95	$105.90
Purchase #5	$170.78	12.614%	$192.3222	$192.32	$192.30	$192.30
Purchase #6	$159.56	11.858%	$178.4806	$178.48	$178.50	$178.50
Purchase #7	$108.28	6.417%	$115.2283	$115.23	$115.25	$115.20
7 purchase totals =	$1,048.57		$1,147.1720	$1,147.17	$1,147.20	$1,147.20