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	$93.88	11.292%	$104.4809	$104.48	$104.50	$104.50
Purchase #2	$146.39	4.206%	$152.5472	$152.55	$152.55	$152.50
Purchase #3	$118.27	13.650%	$134.4139	$134.41	$134.40	$134.40
Purchase #4	$240.73	12.297%	$270.3326	$270.33	$270.35	$270.30
Purchase #5	$38.83	3.318%	$40.1184	$40.12	$40.10	$40.10
Purchase #6	$133.65	10.725%	$147.984	$147.98	$148.00	$148.00
Purchase #7	$200.60	11.869%	$224.4092	$224.41	$224.40	$224.40
7 purchase totals =	$972.35		$1,074.2862	$1,074.28	$1,074.30	$1,074.20