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	$57.38	10.117%	$63.1851	$63.19	$63.20	$63.20
Purchase #2	$244.56	6.864%	$261.3466	$261.35	$261.35	$261.30
Purchase #3	$48.38	13.711%	$55.0134	$55.01	$55.00	$55.00
Purchase #4	$211.67	6.597%	$225.6339	$225.63	$225.65	$225.60
Purchase #5	$42.92	5.134%	$45.1235	$45.12	$45.10	$45.10
Purchase #6	$58.83	4.409%	$61.4238	$61.42	$61.40	$61.40
Purchase #7	$79.80	3.471%	$82.5699	$82.57	$82.55	$82.60
7 purchase totals =	$743.54		$794.2962	$794.29	$794.25	$794.20