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	$142.66	4.290%	$148.7801	$148.78	$148.80	$148.80
Purchase #2	$96.91	5.844%	$102.5734	$102.57	$102.55	$102.60
Purchase #3	$43.55	5.768%	$46.062	$46.06	$46.05	$46.10
Purchase #4	$44.33	6.570%	$47.2425	$47.24	$47.25	$47.20
Purchase #5	$31.47	12.795%	$35.4966	$35.50	$35.50	$35.50
Purchase #6	$58.70	6.285%	$62.3893	$62.39	$62.40	$62.40
Purchase #7	$198.79	13.279%	$225.1873	$225.19	$225.20	$225.20
7 purchase totals =	$616.41		$667.7312	$667.73	$667.75	$667.80