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	$209.55	5.545%	$221.1695	$221.17	$221.15	$221.20
Purchase #2	$96.59	11.109%	$107.3202	$107.32	$107.30	$107.30
Purchase #3	$46.93	4.228%	$48.9142	$48.91	$48.90	$48.90
Purchase #4	$148.46	12.191%	$166.5588	$166.56	$166.55	$166.60
Purchase #5	$154.69	8.213%	$167.3947	$167.39	$167.40	$167.40
Purchase #6	$131.61	12.860%	$148.535	$148.54	$148.55	$148.50
Purchase #7	$241.60	11.360%	$269.0458	$269.05	$269.05	$269.00
7 purchase totals =	$1,029.43		$1,128.9382	$1,128.94	$1,128.90	$1,128.90