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	$64.86	10.712%	$71.8078	$71.81	$71.80	$71.80
Purchase #2	$47.41	12.661%	$53.4126	$53.41	$53.40	$53.40
Purchase #3	$17.27	10.156%	$19.0239	$19.02	$19.00	$19.00
Purchase #4	$60.76	13.813%	$69.1528	$69.15	$69.15	$69.20
Purchase #5	$131.33	9.866%	$144.287	$144.29	$144.30	$144.30
Purchase #6	$172.63	13.708%	$196.2941	$196.29	$196.30	$196.30
Purchase #7	$151.77	13.178%	$171.7703	$171.77	$171.75	$171.80
7 purchase totals =	$646.03		$725.7485	$725.74	$725.70	$725.80