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	$239.96	6.384%	$255.279	$255.28	$255.30	$255.30
Purchase #2	$26.65	10.196%	$29.3672	$29.37	$29.35	$29.40
Purchase #3	$89.97	9.562%	$98.5729	$98.57	$98.55	$98.60
Purchase #4	$37.98	11.556%	$42.369	$42.37	$42.35	$42.40
Purchase #5	$222.39	10.364%	$245.4385	$245.44	$245.45	$245.40
Purchase #6	$197.33	12.764%	$222.5172	$222.52	$222.50	$222.50
Purchase #7	$248.75	7.773%	$268.0853	$268.09	$268.10	$268.10
7 purchase totals =	$1,063.03		$1,161.6291	$1,161.64	$1,161.60	$1,161.70