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	$33.94	9.768%	$37.2553	$37.26	$37.25	$37.30
Purchase #2	$10.30	10.807%	$11.4131	$11.41	$11.40	$11.40
Purchase #3	$165.69	9.133%	$180.8225	$180.82	$180.80	$180.80
Purchase #4	$108.41	10.829%	$120.1497	$120.15	$120.15	$120.10
Purchase #5	$173.72	7.409%	$186.5909	$186.59	$186.60	$186.60
Purchase #6	$53.28	3.444%	$55.115	$55.12	$55.10	$55.10
Purchase #7	$45.77	12.673%	$51.5704	$51.57	$51.55	$51.60
7 purchase totals =	$591.11		$642.9169	$642.92	$642.85	$642.90