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	$58.56	6.424%	$62.3219	$62.32	$62.30	$62.30
Purchase #2	$77.89	10.503%	$86.0708	$86.07	$86.05	$86.10
Purchase #3	$169.55	9.419%	$185.5199	$185.52	$185.50	$185.50
Purchase #4	$132.39	9.585%	$145.0796	$145.08	$145.10	$145.10
Purchase #5	$80.81	3.481%	$83.623	$83.62	$83.60	$83.60
Purchase #6	$54.96	11.503%	$61.282	$61.28	$61.30	$61.30
Purchase #7	$12.62	3.668%	$13.0829	$13.08	$13.10	$13.10
7 purchase totals =	$586.78		$636.9801	$636.97	$636.95	$637.00