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	$93.52	5.678%	$98.8301	$98.83	$98.85	$98.80
Purchase #2	$161.32	11.591%	$180.0186	$180.02	$180.00	$180.00
Purchase #3	$147.49	11.487%	$164.4322	$164.43	$164.45	$164.40
Purchase #4	$116.55	13.663%	$132.4742	$132.47	$132.45	$132.50
Purchase #5	$39.63	4.251%	$41.3147	$41.31	$41.30	$41.30
Purchase #6	$165.94	5.711%	$175.4168	$175.42	$175.40	$175.40
Purchase #7	$238.37	13.872%	$271.4367	$271.44	$271.45	$271.40
7 purchase totals =	$962.82		$1,063.9233	$1,063.92	$1,063.90	$1,063.80