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	$7.36	8.123%	$7.9579	$7.96	$7.95	$8.00
Purchase #2	$165.82	9.672%	$181.8581	$181.86	$181.85	$181.90
Purchase #3	$245.38	8.581%	$266.4361	$266.44	$266.45	$266.40
Purchase #4	$69.32	5.630%	$73.2227	$73.22	$73.20	$73.20
Purchase #5	$142.52	3.653%	$147.7263	$147.73	$147.75	$147.70
Purchase #6	$187.30	4.818%	$196.3241	$196.32	$196.30	$196.30
Purchase #7	$188.90	9.506%	$206.8568	$206.86	$206.85	$206.90
7 purchase totals =	$1,006.60		$1,080.3820	$1,080.39	$1,080.35	$1,080.40