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	$52.82	3.368%	$54.599	$54.60	$54.60	$54.60
Purchase #2	$47.70	12.867%	$53.8376	$53.84	$53.85	$53.80
Purchase #3	$54.44	8.800%	$59.2307	$59.23	$59.25	$59.20
Purchase #4	$30.87	13.579%	$35.0618	$35.06	$35.05	$35.10
Purchase #5	$149.89	8.126%	$162.0701	$162.07	$162.05	$162.10
Purchase #6	$87.79	11.569%	$97.9464	$97.95	$97.95	$97.90
Purchase #7	$186.50	12.758%	$210.2937	$210.29	$210.30	$210.30
7 purchase totals =	$610.01		$673.0393	$673.04	$673.05	$673.00