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	$139.64	6.718%	$149.021	$149.02	$149.00	$149.00
Purchase #2	$208.64	6.822%	$222.8734	$222.87	$222.85	$222.90
Purchase #3	$209.44	11.317%	$233.1423	$233.14	$233.15	$233.10
Purchase #4	$167.32	5.345%	$176.2633	$176.26	$176.25	$176.30
Purchase #5	$77.42	12.300%	$86.9427	$86.94	$86.95	$86.90
Purchase #6	$134.71	7.805%	$145.2241	$145.22	$145.20	$145.20
Purchase #7	$77.80	11.665%	$86.8754	$86.88	$86.90	$86.90
7 purchase totals =	$1,014.97		$1,100.3422	$1,100.33	$1,100.30	$1,100.30