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	$141.94	6.851%	$151.6643	$151.66	$151.65	$151.70
Purchase #2	$30.39	6.290%	$32.3015	$32.30	$32.30	$32.30
Purchase #3	$29.62	5.476%	$31.242	$31.24	$31.25	$31.20
Purchase #4	$103.28	9.318%	$112.9036	$112.90	$112.90	$112.90
Purchase #5	$25.53	9.200%	$27.8788	$27.88	$27.90	$27.90
Purchase #6	$222.76	11.473%	$248.3173	$248.32	$248.30	$248.30
Purchase #7	$99.61	12.200%	$111.7624	$111.76	$111.75	$111.80
7 purchase totals =	$653.13		$716.0699	$716.06	$716.05	$716.10