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	$141.60	9.107%	$154.4955	$154.50	$154.50	$154.50
Purchase #2	$143.42	11.342%	$159.6867	$159.69	$159.70	$159.70
Purchase #3	$6.83	3.436%	$7.0647	$7.06	$7.05	$7.10
Purchase #4	$162.73	12.510%	$183.0875	$183.09	$183.10	$183.10
Purchase #5	$85.36	12.826%	$96.3083	$96.31	$96.30	$96.30
Purchase #6	$118.32	7.434%	$127.1159	$127.12	$127.10	$127.10
Purchase #7	$125.90	9.250%	$137.5458	$137.55	$137.55	$137.50
7 purchase totals =	$784.16		$865.3044	$865.32	$865.30	$865.30