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	$206.44	9.651%	$226.3635	$226.36	$226.35	$226.40
Purchase #2	$82.48	9.811%	$90.5721	$90.57	$90.55	$90.60
Purchase #3	$62.90	13.740%	$71.5425	$71.54	$71.55	$71.50
Purchase #4	$61.32	10.744%	$67.9082	$67.91	$67.90	$67.90
Purchase #5	$145.92	6.873%	$155.9491	$155.95	$155.95	$155.90
Purchase #6	$225.31	6.573%	$240.1196	$240.12	$240.10	$240.10
Purchase #7	$161.44	5.568%	$170.429	$170.43	$170.45	$170.40
7 purchase totals =	$945.81		$1,022.8840	$1,022.88	$1,022.85	$1,022.80