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	$150.46	10.181%	$165.7783	$165.78	$165.80	$165.80
Purchase #2	$170.37	4.671%	$178.328	$178.33	$178.35	$178.30
Purchase #3	$73.54	11.676%	$82.1265	$82.13	$82.15	$82.10
Purchase #4	$91.25	9.745%	$100.1423	$100.14	$100.15	$100.10
Purchase #5	$92.63	6.173%	$98.348	$98.35	$98.35	$98.30
Purchase #6	$235.87	5.507%	$248.8594	$248.86	$248.85	$248.90
Purchase #7	$68.39	7.342%	$73.4112	$73.41	$73.40	$73.40
7 purchase totals =	$882.51		$946.9937	$947.00	$947.05	$946.90