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	$173.52	13.447%	$196.8532	$196.85	$196.85	$196.90
Purchase #2	$242.26	9.121%	$264.3565	$264.36	$264.35	$264.40
Purchase #3	$150.39	9.494%	$164.668	$164.67	$164.65	$164.70
Purchase #4	$154.89	3.582%	$160.4382	$160.44	$160.45	$160.40
Purchase #5	$142.94	6.727%	$152.5556	$152.56	$152.55	$152.60
Purchase #6	$94.88	4.512%	$99.161	$99.16	$99.15	$99.20
Purchase #7	$221.40	4.215%	$230.732	$230.73	$230.75	$230.70
7 purchase totals =	$1,180.28		$1,268.7645	$1,268.77	$1,268.75	$1,268.90