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	$229.33	9.471%	$251.0498	$251.05	$251.05	$251.00
Purchase #2	$207.99	10.269%	$229.3485	$229.35	$229.35	$229.30
Purchase #3	$57.44	9.591%	$62.9491	$62.95	$62.95	$62.90
Purchase #4	$89.53	12.384%	$100.6174	$100.62	$100.60	$100.60
Purchase #5	$180.32	8.463%	$195.5805	$195.58	$195.60	$195.60
Purchase #6	$86.61	5.631%	$91.487	$91.49	$91.50	$91.50
Purchase #7	$78.26	10.525%	$86.4969	$86.50	$86.50	$86.50
7 purchase totals =	$929.48		$1,017.5292	$1,017.54	$1,017.55	$1,017.40