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	$147.58	11.140%	$164.0204	$164.02	$164.00	$164.00
Purchase #2	$229.34	9.722%	$251.6364	$251.64	$251.65	$251.60
Purchase #3	$58.67	11.453%	$65.3895	$65.39	$65.40	$65.40
Purchase #4	$64.77	4.799%	$67.8783	$67.88	$67.90	$67.90
Purchase #5	$93.39	4.367%	$97.4683	$97.47	$97.45	$97.50
Purchase #6	$36.78	3.685%	$38.1353	$38.14	$38.15	$38.10
Purchase #7	$80.95	10.135%	$89.1543	$89.15	$89.15	$89.20
7 purchase totals =	$711.48		$773.6825	$773.69	$773.70	$773.70