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	$158.73	3.659%	$164.5379	$164.54	$164.55	$164.50
Purchase #2	$165.73	3.371%	$171.3168	$171.32	$171.30	$171.30
Purchase #3	$147.66	4.223%	$153.8957	$153.90	$153.90	$153.90
Purchase #4	$106.69	4.270%	$111.2457	$111.25	$111.25	$111.20
Purchase #5	$232.93	7.329%	$250.0014	$250.00	$250.00	$250.00
Purchase #6	$137.31	11.166%	$152.642	$152.64	$152.65	$152.60
Purchase #7	$118.91	4.239%	$123.9506	$123.95	$123.95	$124.00
7 purchase totals =	$1,067.96		$1,127.5901	$1,127.60	$1,127.60	$1,127.50