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	$90.59	12.298%	$101.7308	$101.73	$101.75	$101.70
Purchase #2	$194.83	5.439%	$205.4268	$205.43	$205.45	$205.40
Purchase #3	$230.50	11.818%	$257.7405	$257.74	$257.75	$257.70
Purchase #4	$35.68	13.506%	$40.4989	$40.50	$40.50	$40.50
Purchase #5	$140.36	5.820%	$148.529	$148.53	$148.55	$148.50
Purchase #6	$165.50	6.662%	$176.5256	$176.53	$176.55	$176.50
Purchase #7	$80.59	5.866%	$85.3174	$85.32	$85.30	$85.30
7 purchase totals =	$938.05		$1,015.7690	$1,015.78	$1,015.85	$1,015.60