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	$93.90	11.385%	$104.5905	$104.59	$104.60	$104.60
Purchase #2	$141.85	6.368%	$150.883	$150.88	$150.90	$150.90
Purchase #3	$97.26	12.807%	$109.7161	$109.72	$109.70	$109.70
Purchase #4	$55.33	7.123%	$59.2712	$59.27	$59.25	$59.30
Purchase #5	$142.86	12.151%	$160.2189	$160.22	$160.20	$160.20
Purchase #6	$13.81	7.227%	$14.808	$14.81	$14.80	$14.80
Purchase #7	$144.82	10.349%	$159.8074	$159.81	$159.80	$159.80
7 purchase totals =	$689.83		$759.2951	$759.30	$759.25	$759.30