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	$243.91	8.499%	$264.6399	$264.64	$264.65	$264.60
Purchase #2	$100.31	5.477%	$105.804	$105.80	$105.80	$105.80
Purchase #3	$69.46	5.562%	$73.3234	$73.32	$73.30	$73.30
Purchase #4	$98.89	7.525%	$106.3315	$106.33	$106.35	$106.30
Purchase #5	$230.78	13.629%	$262.233	$262.23	$262.25	$262.20
Purchase #6	$156.35	11.775%	$174.7602	$174.76	$174.75	$174.80
Purchase #7	$100.86	11.649%	$112.6092	$112.61	$112.60	$112.60
7 purchase totals =	$1,000.56		$1,099.7012	$1,099.69	$1,099.70	$1,099.60