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	$156.26	5.868%	$165.4293	$165.43	$165.45	$165.40
Purchase #2	$127.53	5.524%	$134.5748	$134.57	$134.55	$134.60
Purchase #3	$205.45	3.254%	$212.1353	$212.14	$212.15	$212.10
Purchase #4	$31.46	5.753%	$33.2699	$33.27	$33.25	$33.30
Purchase #5	$92.85	4.241%	$96.7878	$96.79	$96.80	$96.80
Purchase #6	$180.93	7.394%	$194.308	$194.31	$194.30	$194.30
Purchase #7	$88.91	12.776%	$100.2691	$100.27	$100.25	$100.30
7 purchase totals =	$883.39		$936.7742	$936.78	$936.75	$936.80