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	$234.82	8.319%	$254.3547	$254.35	$254.35	$254.40
Purchase #2	$95.62	9.128%	$104.3482	$104.35	$104.35	$104.30
Purchase #3	$223.82	9.673%	$245.4701	$245.47	$245.45	$245.50
Purchase #4	$88.76	13.402%	$100.6556	$100.66	$100.65	$100.70
Purchase #5	$88.70	12.610%	$99.8851	$99.89	$99.90	$99.90
Purchase #6	$32.42	8.788%	$35.2691	$35.27	$35.25	$35.30
Purchase #7	$181.91	8.207%	$196.8394	$196.84	$196.85	$196.80
7 purchase totals =	$946.05		$1,036.8222	$1,036.83	$1,036.80	$1,036.90