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	$114.66	13.345%	$129.9614	$129.96	$129.95	$130.00
Purchase #2	$30.78	3.473%	$31.849	$31.85	$31.85	$31.80
Purchase #3	$160.64	11.628%	$179.3192	$179.32	$179.30	$179.30
Purchase #4	$67.50	7.616%	$72.6408	$72.64	$72.65	$72.60
Purchase #5	$123.74	3.244%	$127.7541	$127.75	$127.75	$127.80
Purchase #6	$44.98	11.601%	$50.1981	$50.20	$50.20	$50.20
Purchase #7	$111.61	7.119%	$119.5555	$119.56	$119.55	$119.60
7 purchase totals =	$653.91		$711.2781	$711.28	$711.25	$711.30