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	$88.34	7.773%	$95.2067	$95.21	$95.20	$95.20
Purchase #2	$196.42	4.772%	$205.7932	$205.79	$205.80	$205.80
Purchase #3	$124.40	5.321%	$131.0193	$131.02	$131.00	$131.00
Purchase #4	$144.90	13.362%	$164.2615	$164.26	$164.25	$164.30
Purchase #5	$161.50	9.194%	$176.3483	$176.35	$176.35	$176.30
Purchase #6	$94.90	6.133%	$100.7202	$100.72	$100.70	$100.70
Purchase #7	$233.56	4.462%	$243.9814	$243.98	$244.00	$244.00
7 purchase totals =	$1,044.02		$1,117.3306	$1,117.33	$1,117.30	$1,117.30