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	$242.41	8.852%	$263.8681	$263.87	$263.85	$263.90
Purchase #2	$173.35	5.271%	$182.4873	$182.49	$182.50	$182.50
Purchase #3	$232.38	11.631%	$259.4081	$259.41	$259.40	$259.40
Purchase #4	$14.84	3.250%	$15.3223	$15.32	$15.30	$15.30
Purchase #5	$155.63	7.616%	$167.4828	$167.48	$167.50	$167.50
Purchase #6	$185.52	12.683%	$209.0495	$209.05	$209.05	$209.00
Purchase #7	$30.55	9.374%	$33.4138	$33.41	$33.40	$33.40
7 purchase totals =	$1,034.68		$1,131.0319	$1,131.03	$1,131.00	$1,131.00