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	$119.85	7.401%	$128.7201	$128.72	$128.70	$128.70
Purchase #2	$96.61	7.711%	$104.0596	$104.06	$104.05	$104.10
Purchase #3	$176.80	11.358%	$196.8809	$196.88	$196.90	$196.90
Purchase #4	$170.46	9.275%	$186.2702	$186.27	$186.25	$186.30
Purchase #5	$51.64	13.608%	$58.6672	$58.67	$58.65	$58.70
Purchase #6	$40.29	3.355%	$41.6417	$41.64	$41.65	$41.60
Purchase #7	$85.52	10.450%	$94.4568	$94.46	$94.45	$94.50
7 purchase totals =	$741.17		$810.6965	$810.70	$810.65	$810.80