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	$181.78	6.380%	$193.3776	$193.38	$193.40	$193.40
Purchase #2	$216.27	10.270%	$238.4809	$238.48	$238.50	$238.50
Purchase #3	$177.83	5.632%	$187.8454	$187.85	$187.85	$187.80
Purchase #4	$176.26	10.191%	$194.2227	$194.22	$194.20	$194.20
Purchase #5	$104.70	6.107%	$111.094	$111.09	$111.10	$111.10
Purchase #6	$88.32	6.809%	$94.3337	$94.33	$94.35	$94.30
Purchase #7	$199.87	11.127%	$222.1095	$222.11	$222.10	$222.10
7 purchase totals =	$1,145.03		$1,241.4638	$1,241.46	$1,241.50	$1,241.40