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	$228.83	4.593%	$239.3402	$239.34	$239.35	$239.30
Purchase #2	$171.71	6.502%	$182.8746	$182.87	$182.85	$182.90
Purchase #3	$34.46	4.771%	$36.1041	$36.10	$36.10	$36.10
Purchase #4	$226.89	11.764%	$253.5813	$253.58	$253.60	$253.60
Purchase #5	$181.41	5.362%	$191.1372	$191.14	$191.15	$191.10
Purchase #6	$164.73	3.823%	$171.0276	$171.03	$171.05	$171.00
Purchase #7	$52.68	12.506%	$59.2682	$59.27	$59.25	$59.30
7 purchase totals =	$1,060.71		$1,133.3332	$1,133.33	$1,133.35	$1,133.30