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	$50.65	11.782%	$56.6176	$56.62	$56.60	$56.60
Purchase #2	$165.27	3.749%	$171.466	$171.47	$171.45	$171.50
Purchase #3	$195.88	13.611%	$222.5412	$222.54	$222.55	$222.50
Purchase #4	$82.97	10.211%	$91.4421	$91.44	$91.45	$91.40
Purchase #5	$250.51	6.535%	$266.8808	$266.88	$266.90	$266.90
Purchase #6	$196.29	8.676%	$213.3201	$213.32	$213.30	$213.30
Purchase #7	$119.77	8.660%	$130.1421	$130.14	$130.15	$130.10
7 purchase totals =	$1,061.34		$1,152.4099	$1,152.41	$1,152.40	$1,152.30