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	$180.99	11.761%	$202.2762	$202.28	$202.30	$202.30
Purchase #2	$191.40	11.392%	$213.2043	$213.20	$213.20	$213.20
Purchase #3	$54.84	8.402%	$59.4477	$59.45	$59.45	$59.40
Purchase #4	$103.31	6.383%	$109.9043	$109.90	$109.90	$109.90
Purchase #5	$183.51	9.403%	$200.7654	$200.77	$200.75	$200.80
Purchase #6	$223.66	6.574%	$238.3634	$238.36	$238.35	$238.40
Purchase #7	$144.37	4.166%	$150.3845	$150.38	$150.40	$150.40
7 purchase totals =	$1,082.08		$1,174.3458	$1,174.34	$1,174.35	$1,174.40