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	$91.37	12.130%	$102.4532	$102.45	$102.45	$102.50
Purchase #2	$91.32	8.621%	$99.1927	$99.19	$99.20	$99.20
Purchase #3	$86.49	9.708%	$94.8864	$94.89	$94.90	$94.90
Purchase #4	$222.90	12.794%	$251.4178	$251.42	$251.40	$251.40
Purchase #5	$65.27	7.113%	$69.9127	$69.91	$69.90	$69.90
Purchase #6	$233.30	3.125%	$240.5906	$240.59	$240.60	$240.60
Purchase #7	$196.54	3.826%	$204.0596	$204.06	$204.05	$204.10
7 purchase totals =	$987.19		$1,062.5130	$1,062.51	$1,062.50	$1,062.60