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	$169.83	6.357%	$180.6261	$180.63	$180.65	$180.60
Purchase #2	$78.34	13.445%	$88.8728	$88.87	$88.85	$88.90
Purchase #3	$177.77	7.488%	$191.0814	$191.08	$191.10	$191.10
Purchase #4	$196.81	9.410%	$215.3298	$215.33	$215.35	$215.30
Purchase #5	$236.84	11.729%	$264.619	$264.62	$264.60	$264.60
Purchase #6	$162.86	5.526%	$171.8596	$171.86	$171.85	$171.90
Purchase #7	$198.94	3.809%	$206.5176	$206.52	$206.50	$206.50
7 purchase totals =	$1,221.39		$1,318.9063	$1,318.91	$1,318.90	$1,318.90