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	$93.77	3.200%	$96.7706	$96.77	$96.75	$96.80
Purchase #2	$62.61	13.829%	$71.2683	$71.27	$71.25	$71.30
Purchase #3	$123.42	6.853%	$131.878	$131.88	$131.90	$131.90
Purchase #4	$28.38	9.722%	$31.1391	$31.14	$31.15	$31.10
Purchase #5	$89.70	5.221%	$94.3832	$94.38	$94.40	$94.40
Purchase #6	$36.50	6.841%	$38.997	$39.00	$39.00	$39.00
Purchase #7	$213.71	4.763%	$223.889	$223.89	$223.90	$223.90
7 purchase totals =	$648.09		$688.3252	$688.33	$688.35	$688.40