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	$148.71	9.261%	$162.482	$162.48	$162.50	$162.50
Purchase #2	$91.33	11.565%	$101.8923	$101.89	$101.90	$101.90
Purchase #3	$24.72	4.465%	$25.8237	$25.82	$25.80	$25.80
Purchase #4	$85.98	5.382%	$90.6074	$90.61	$90.60	$90.60
Purchase #5	$168.82	9.272%	$184.473	$184.47	$184.45	$184.50
Purchase #6	$235.74	11.857%	$263.6917	$263.69	$263.70	$263.70
Purchase #7	$20.89	11.565%	$23.3059	$23.31	$23.30	$23.30
7 purchase totals =	$776.19		$852.2760	$852.27	$852.25	$852.30