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	$204.89	5.353%	$215.8578	$215.86	$215.85	$215.90
Purchase #2	$248.84	9.715%	$273.0148	$273.01	$273.00	$273.00
Purchase #3	$245.33	7.250%	$263.1164	$263.12	$263.10	$263.10
Purchase #4	$79.64	13.851%	$90.6709	$90.67	$90.65	$90.70
Purchase #5	$120.86	4.114%	$125.8322	$125.83	$125.85	$125.80
Purchase #6	$85.98	5.314%	$90.549	$90.55	$90.55	$90.50
Purchase #7	$31.58	11.571%	$35.2341	$35.23	$35.25	$35.20
7 purchase totals =	$1,017.12		$1,094.2752	$1,094.27	$1,094.25	$1,094.20