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	$147.59	3.696%	$153.0449	$153.04	$153.05	$153.00
Purchase #2	$130.60	11.816%	$146.0317	$146.03	$146.05	$146.00
Purchase #3	$150.64	11.643%	$168.179	$168.18	$168.20	$168.20
Purchase #4	$99.47	11.529%	$110.9379	$110.94	$110.95	$110.90
Purchase #5	$49.37	6.375%	$52.5173	$52.52	$52.50	$52.50
Purchase #6	$96.65	7.246%	$103.6533	$103.65	$103.65	$103.70
Purchase #7	$186.88	11.240%	$207.8853	$207.89	$207.90	$207.90
7 purchase totals =	$861.20		$942.2494	$942.25	$942.30	$942.20