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	$152.73	9.523%	$167.2745	$167.27	$167.25	$167.30
Purchase #2	$140.41	6.300%	$149.2558	$149.26	$149.25	$149.30
Purchase #3	$71.84	11.483%	$80.0894	$80.09	$80.10	$80.10
Purchase #4	$46.45	6.765%	$49.5923	$49.59	$49.60	$49.60
Purchase #5	$219.40	6.400%	$233.4416	$233.44	$233.45	$233.40
Purchase #6	$203.73	13.116%	$230.4512	$230.45	$230.45	$230.50
Purchase #7	$90.81	9.443%	$99.3852	$99.39	$99.40	$99.40
7 purchase totals =	$925.37		$1,009.4900	$1,009.49	$1,009.50	$1,009.60