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	$19.36	13.460%	$21.9659	$21.97	$21.95	$22.00
Purchase #2	$138.85	9.419%	$151.9283	$151.93	$151.95	$151.90
Purchase #3	$125.69	7.736%	$135.4134	$135.41	$135.40	$135.40
Purchase #4	$33.38	11.789%	$37.3152	$37.32	$37.30	$37.30
Purchase #5	$79.55	3.799%	$82.5721	$82.57	$82.55	$82.60
Purchase #6	$63.62	11.593%	$70.9955	$71.00	$71.00	$71.00
Purchase #7	$64.75	11.337%	$72.0907	$72.09	$72.10	$72.10
7 purchase totals =	$525.20		$572.2811	$572.29	$572.25	$572.30