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	$220.26	10.800%	$244.0481	$244.05	$244.05	$244.00
Purchase #2	$108.46	3.778%	$112.5576	$112.56	$112.55	$112.60
Purchase #3	$159.48	8.793%	$173.5031	$173.50	$173.50	$173.50
Purchase #4	$45.65	3.674%	$47.3272	$47.33	$47.35	$47.30
Purchase #5	$191.86	8.355%	$207.8899	$207.89	$207.90	$207.90
Purchase #6	$139.54	3.738%	$144.756	$144.76	$144.75	$144.80
Purchase #7	$137.91	6.229%	$146.5004	$146.50	$146.50	$146.50
7 purchase totals =	$1,003.16		$1,076.5823	$1,076.59	$1,076.60	$1,076.60