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	$101.98	3.611%	$105.6625	$105.66	$105.65	$105.70
Purchase #2	$189.44	4.722%	$198.3854	$198.39	$198.40	$198.40
Purchase #3	$172.79	10.678%	$191.2405	$191.24	$191.25	$191.20
Purchase #4	$117.53	8.229%	$127.2015	$127.20	$127.20	$127.20
Purchase #5	$180.37	3.636%	$186.9283	$186.93	$186.95	$186.90
Purchase #6	$183.28	3.588%	$189.8561	$189.86	$189.85	$189.90
Purchase #7	$43.40	7.314%	$46.5743	$46.57	$46.55	$46.60
7 purchase totals =	$988.79		$1,045.8486	$1,045.85	$1,045.85	$1,045.90