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	$10.76	4.490%	$11.2431	$11.24	$11.25	$11.20
Purchase #2	$64.43	5.359%	$67.8828	$67.88	$67.90	$67.90
Purchase #3	$203.95	6.320%	$216.8396	$216.84	$216.85	$216.80
Purchase #4	$186.76	9.470%	$204.4462	$204.45	$204.45	$204.40
Purchase #5	$166.77	3.515%	$172.632	$172.63	$172.65	$172.60
Purchase #6	$144.90	3.805%	$150.4134	$150.41	$150.40	$150.40
Purchase #7	$164.41	9.269%	$179.6492	$179.65	$179.65	$179.60
7 purchase totals =	$941.98		$1,003.1063	$1,003.10	$1,003.15	$1,002.90