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	$178.47	3.815%	$185.2786	$185.28	$185.30	$185.30
Purchase #2	$141.57	9.656%	$155.24	$155.24	$155.25	$155.20
Purchase #3	$118.33	9.397%	$129.4495	$129.45	$129.45	$129.40
Purchase #4	$78.45	9.559%	$85.949	$85.95	$85.95	$85.90
Purchase #5	$206.59	6.756%	$220.5472	$220.55	$220.55	$220.50
Purchase #6	$143.36	6.411%	$152.5508	$152.55	$152.55	$152.60
Purchase #7	$225.86	3.181%	$233.0446	$233.04	$233.05	$233.00
7 purchase totals =	$1,092.63		$1,162.0597	$1,162.06	$1,162.10	$1,161.90