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	$201.82	3.822%	$209.5336	$209.53	$209.55	$209.50
Purchase #2	$219.83	6.665%	$234.4817	$234.48	$234.50	$234.50
Purchase #3	$89.40	11.567%	$99.7409	$99.74	$99.75	$99.70
Purchase #4	$51.35	8.710%	$55.8226	$55.82	$55.80	$55.80
Purchase #5	$226.38	11.814%	$253.1245	$253.12	$253.10	$253.10
Purchase #6	$202.59	5.524%	$213.7811	$213.78	$213.80	$213.80
Purchase #7	$148.46	12.852%	$167.5401	$167.54	$167.55	$167.50
7 purchase totals =	$1,139.83		$1,234.0245	$1,234.01	$1,234.05	$1,233.90