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	$187.69	4.152%	$195.4829	$195.48	$195.50	$195.50
Purchase #2	$234.38	3.205%	$241.8919	$241.89	$241.90	$241.90
Purchase #3	$248.46	4.546%	$259.755	$259.76	$259.75	$259.80
Purchase #4	$91.97	8.622%	$99.8997	$99.90	$99.90	$99.90
Purchase #5	$17.43	3.704%	$18.0756	$18.08	$18.10	$18.10
Purchase #6	$249.27	10.676%	$275.8821	$275.88	$275.90	$275.90
Purchase #7	$18.68	9.293%	$20.4159	$20.42	$20.40	$20.40
7 purchase totals =	$1,047.88		$1,111.4031	$1,111.41	$1,111.45	$1,111.50