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	$180.27	4.204%	$187.8486	$187.85	$187.85	$187.80
Purchase #2	$176.98	6.277%	$188.089	$188.09	$188.10	$188.10
Purchase #3	$146.25	13.575%	$166.1034	$166.10	$166.10	$166.10
Purchase #4	$89.44	11.696%	$99.9009	$99.90	$99.90	$99.90
Purchase #5	$198.55	8.755%	$215.9331	$215.93	$215.95	$215.90
Purchase #6	$135.87	6.466%	$144.6554	$144.66	$144.65	$144.70
Purchase #7	$69.53	5.788%	$73.5544	$73.55	$73.55	$73.60
7 purchase totals =	$996.89		$1,076.0848	$1,076.08	$1,076.10	$1,076.10