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	$58.46	7.630%	$62.9205	$62.92	$62.90	$62.90
Purchase #2	$106.78	7.764%	$115.0704	$115.07	$115.05	$115.10
Purchase #3	$98.60	5.307%	$103.8327	$103.83	$103.85	$103.80
Purchase #4	$189.35	13.636%	$215.1698	$215.17	$215.15	$215.20
Purchase #5	$188.29	4.421%	$196.6143	$196.61	$196.60	$196.60
Purchase #6	$245.48	11.270%	$273.1456	$273.15	$273.15	$273.10
Purchase #7	$5.55	4.622%	$5.8065	$5.81	$5.80	$5.80
7 purchase totals =	$892.51		$972.5598	$972.56	$972.50	$972.50