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	$98.98	8.799%	$107.6893	$107.69	$107.70	$107.70
Purchase #2	$99.60	13.191%	$112.7382	$112.74	$112.75	$112.70
Purchase #3	$122.48	13.738%	$139.3063	$139.31	$139.30	$139.30
Purchase #4	$218.70	13.208%	$247.5859	$247.59	$247.60	$247.60
Purchase #5	$122.98	13.803%	$139.9549	$139.95	$139.95	$140.00
Purchase #6	$171.93	7.838%	$185.4059	$185.41	$185.40	$185.40
Purchase #7	$118.68	8.464%	$128.7251	$128.73	$128.75	$128.70
7 purchase totals =	$953.35		$1,061.4056	$1,061.42	$1,061.45	$1,061.40