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	$228.41	7.414%	$245.3443	$245.34	$245.35	$245.30
Purchase #2	$82.46	8.449%	$89.427	$89.43	$89.45	$89.40
Purchase #3	$43.39	7.804%	$46.7762	$46.78	$46.80	$46.80
Purchase #4	$170.81	9.672%	$187.3307	$187.33	$187.35	$187.30
Purchase #5	$172.43	4.246%	$179.7514	$179.75	$179.75	$179.80
Purchase #6	$156.40	7.653%	$168.3693	$168.37	$168.35	$168.40
Purchase #7	$8.40	11.446%	$9.3615	$9.36	$9.35	$9.40
7 purchase totals =	$862.30		$926.3604	$926.36	$926.40	$926.40