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	$196.90	13.208%	$222.9066	$222.91	$222.90	$222.90
Purchase #2	$157.92	13.212%	$178.7844	$178.78	$178.80	$178.80
Purchase #3	$245.39	7.764%	$264.4421	$264.44	$264.45	$264.40
Purchase #4	$131.88	5.331%	$138.9105	$138.91	$138.90	$138.90
Purchase #5	$180.41	3.270%	$186.3094	$186.31	$186.30	$186.30
Purchase #6	$55.33	11.531%	$61.7101	$61.71	$61.70	$61.70
Purchase #7	$20.34	5.536%	$21.466	$21.47	$21.45	$21.50
7 purchase totals =	$988.17		$1,074.5291	$1,074.53	$1,074.50	$1,074.50