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	$86.35	13.836%	$98.2974	$98.30	$98.30	$98.30
Purchase #2	$205.30	4.627%	$214.7992	$214.80	$214.80	$214.80
Purchase #3	$42.50	10.515%	$46.9689	$46.97	$46.95	$47.00
Purchase #4	$54.58	9.867%	$59.9654	$59.97	$59.95	$60.00
Purchase #5	$77.41	4.488%	$80.8842	$80.88	$80.90	$80.90
Purchase #6	$152.72	6.576%	$162.7629	$162.76	$162.75	$162.80
Purchase #7	$153.54	11.413%	$171.0635	$171.06	$171.05	$171.10
7 purchase totals =	$772.40		$834.7415	$834.74	$834.70	$834.90