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	$65.79	4.390%	$68.6782	$68.68	$68.70	$68.70
Purchase #2	$138.52	13.512%	$157.2368	$157.24	$157.25	$157.20
Purchase #3	$220.56	10.152%	$242.9513	$242.95	$242.95	$243.00
Purchase #4	$119.86	9.104%	$130.7721	$130.77	$130.75	$130.80
Purchase #5	$52.90	7.631%	$56.9368	$56.94	$56.95	$56.90
Purchase #6	$184.81	6.272%	$196.4013	$196.40	$196.40	$196.40
Purchase #7	$89.86	12.280%	$100.8948	$100.89	$100.90	$100.90
7 purchase totals =	$872.30		$953.8713	$953.87	$953.90	$953.90