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	$33.56	4.298%	$35.0024	$35.00	$35.00	$35.00
Purchase #2	$80.50	10.359%	$88.839	$88.84	$88.85	$88.80
Purchase #3	$205.33	3.222%	$211.9457	$211.95	$211.95	$211.90
Purchase #4	$57.85	3.400%	$59.8169	$59.82	$59.80	$59.80
Purchase #5	$166.65	12.166%	$186.9246	$186.92	$186.90	$186.90
Purchase #6	$112.44	11.467%	$125.3335	$125.33	$125.35	$125.30
Purchase #7	$99.94	12.436%	$112.3685	$112.37	$112.35	$112.40
7 purchase totals =	$756.27		$820.2306	$820.23	$820.20	$820.10