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	$120.76	6.538%	$128.6553	$128.66	$128.65	$128.70
Purchase #2	$163.74	5.246%	$172.3298	$172.33	$172.35	$172.30
Purchase #3	$243.32	12.376%	$273.4333	$273.43	$273.45	$273.40
Purchase #4	$148.80	3.788%	$154.4365	$154.44	$154.45	$154.40
Purchase #5	$54.80	8.204%	$59.2958	$59.30	$59.30	$59.30
Purchase #6	$52.70	13.403%	$59.7634	$59.76	$59.75	$59.80
Purchase #7	$188.27	5.162%	$197.9885	$197.99	$198.00	$198.00
7 purchase totals =	$972.39		$1,045.9026	$1,045.91	$1,045.95	$1,045.90