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	$173.56	13.422%	$196.8552	$196.86	$196.85	$196.90
Purchase #2	$25.65	13.370%	$29.0794	$29.08	$29.10	$29.10
Purchase #3	$34.80	10.444%	$38.4345	$38.43	$38.45	$38.40
Purchase #4	$38.78	9.871%	$42.608	$42.61	$42.60	$42.60
Purchase #5	$183.30	6.739%	$195.6526	$195.65	$195.65	$195.70
Purchase #6	$124.59	3.256%	$128.6467	$128.65	$128.65	$128.60
Purchase #7	$147.61	9.402%	$161.4883	$161.49	$161.50	$161.50
7 purchase totals =	$728.29		$792.7647	$792.77	$792.80	$792.80