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	$40.46	11.437%	$45.0874	$45.09	$45.10	$45.10
Purchase #2	$25.77	4.830%	$27.0147	$27.01	$27.00	$27.00
Purchase #3	$169.75	10.221%	$187.1001	$187.10	$187.10	$187.10
Purchase #4	$184.50	3.872%	$191.6438	$191.64	$191.65	$191.60
Purchase #5	$157.80	6.150%	$167.5047	$167.50	$167.50	$167.50
Purchase #6	$158.91	3.372%	$164.2684	$164.27	$164.25	$164.30
Purchase #7	$238.46	3.694%	$247.2687	$247.27	$247.25	$247.30
7 purchase totals =	$975.65		$1,029.8878	$1,029.88	$1,029.85	$1,029.90