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	$83.41	12.705%	$94.0072	$94.01	$94.00	$94.00
Purchase #2	$169.94	10.661%	$188.0573	$188.06	$188.05	$188.10
Purchase #3	$102.92	9.675%	$112.8775	$112.88	$112.90	$112.90
Purchase #4	$142.53	9.612%	$156.23	$156.23	$156.25	$156.20
Purchase #5	$50.73	10.162%	$55.8852	$55.89	$55.90	$55.90
Purchase #6	$227.37	3.146%	$234.5231	$234.52	$234.50	$234.50
Purchase #7	$50.45	5.145%	$53.0457	$53.05	$53.05	$53.00
7 purchase totals =	$827.35		$894.6260	$894.64	$894.65	$894.60