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	$69.81	4.516%	$72.9626	$72.96	$72.95	$73.00
Purchase #2	$137.48	13.697%	$156.3106	$156.31	$156.30	$156.30
Purchase #3	$108.79	9.415%	$119.0326	$119.03	$119.05	$119.00
Purchase #4	$5.70	8.844%	$6.2041	$6.20	$6.20	$6.20
Purchase #5	$84.31	6.549%	$89.8315	$89.83	$89.85	$89.80
Purchase #6	$139.32	9.591%	$152.6822	$152.68	$152.70	$152.70
Purchase #7	$184.96	6.272%	$196.5607	$196.56	$196.55	$196.60
7 purchase totals =	$730.37		$793.5843	$793.57	$793.60	$793.60