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	$183.89	3.701%	$190.6958	$190.70	$190.70	$190.70
Purchase #2	$176.88	12.658%	$199.2695	$199.27	$199.25	$199.30
Purchase #3	$237.90	3.301%	$245.7531	$245.75	$245.75	$245.80
Purchase #4	$40.73	7.706%	$43.8687	$43.87	$43.85	$43.90
Purchase #5	$167.76	8.552%	$182.1068	$182.11	$182.10	$182.10
Purchase #6	$191.76	3.377%	$198.2357	$198.24	$198.25	$198.20
Purchase #7	$32.91	11.745%	$36.7753	$36.78	$36.80	$36.80
7 purchase totals =	$1,031.83		$1,096.7049	$1,096.72	$1,096.70	$1,096.80