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	$167.97	12.681%	$189.2703	$189.27	$189.25	$189.30
Purchase #2	$65.36	9.322%	$71.4529	$71.45	$71.45	$71.50
Purchase #3	$147.73	3.337%	$152.6598	$152.66	$152.65	$152.70
Purchase #4	$88.97	12.850%	$100.4026	$100.40	$100.40	$100.40
Purchase #5	$121.29	6.580%	$129.2709	$129.27	$129.25	$129.30
Purchase #6	$238.80	3.649%	$247.5138	$247.51	$247.50	$247.50
Purchase #7	$159.70	4.748%	$167.2826	$167.28	$167.30	$167.30
7 purchase totals =	$989.82		$1,057.8529	$1,057.84	$1,057.80	$1,058.00