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	$176.33	12.717%	$198.7539	$198.75	$198.75	$198.80
Purchase #2	$7.49	12.469%	$8.4239	$8.42	$8.40	$8.40
Purchase #3	$70.98	10.836%	$78.6714	$78.67	$78.65	$78.70
Purchase #4	$199.93	10.254%	$220.4308	$220.43	$220.45	$220.40
Purchase #5	$111.89	11.607%	$124.8771	$124.88	$124.90	$124.90
Purchase #6	$53.46	10.543%	$59.0963	$59.10	$59.10	$59.10
Purchase #7	$54.76	13.115%	$61.9418	$61.94	$61.95	$61.90
7 purchase totals =	$674.84		$752.1952	$752.19	$752.20	$752.20