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	$71.74	9.210%	$78.3473	$78.35	$78.35	$78.30
Purchase #2	$16.70	9.463%	$18.2803	$18.28	$18.30	$18.30
Purchase #3	$57.98	12.621%	$65.2977	$65.30	$65.30	$65.30
Purchase #4	$219.85	12.651%	$247.6632	$247.66	$247.65	$247.70
Purchase #5	$8.85	11.843%	$9.8981	$9.90	$9.90	$9.90
Purchase #6	$200.49	12.372%	$225.2946	$225.29	$225.30	$225.30
Purchase #7	$45.70	6.741%	$48.7806	$48.78	$48.80	$48.80
7 purchase totals =	$621.31		$693.5618	$693.56	$693.60	$693.60