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	$85.62	13.616%	$97.278	$97.28	$97.30	$97.30
Purchase #2	$51.98	5.859%	$55.0255	$55.03	$55.05	$55.00
Purchase #3	$135.93	6.865%	$145.2616	$145.26	$145.25	$145.30
Purchase #4	$50.83	7.440%	$54.6118	$54.61	$54.60	$54.60
Purchase #5	$130.60	4.436%	$136.3934	$136.39	$136.40	$136.40
Purchase #6	$111.45	7.825%	$120.171	$120.17	$120.15	$120.20
Purchase #7	$71.33	10.174%	$78.5871	$78.59	$78.60	$78.60
7 purchase totals =	$637.74		$687.3284	$687.33	$687.35	$687.40