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	$149.60	11.831%	$167.2992	$167.30	$167.30	$167.30
Purchase #2	$33.72	11.611%	$37.6352	$37.64	$37.65	$37.60
Purchase #3	$150.36	3.695%	$155.9158	$155.92	$155.90	$155.90
Purchase #4	$158.59	12.840%	$178.953	$178.95	$178.95	$179.00
Purchase #5	$121.89	4.556%	$127.4433	$127.44	$127.45	$127.40
Purchase #6	$191.97	8.801%	$208.8653	$208.87	$208.85	$208.90
Purchase #7	$223.33	12.348%	$250.9068	$250.91	$250.90	$250.90
7 purchase totals =	$1,029.46		$1,127.0186	$1,127.03	$1,127.00	$1,127.00