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	$85.54	5.582%	$90.3148	$90.31	$90.30	$90.30
Purchase #2	$175.95	6.458%	$187.3129	$187.31	$187.30	$187.30
Purchase #3	$225.85	12.584%	$254.271	$254.27	$254.25	$254.30
Purchase #4	$188.92	11.159%	$210.0016	$210.00	$210.00	$210.00
Purchase #5	$185.65	3.632%	$192.3928	$192.39	$192.40	$192.40
Purchase #6	$102.98	9.428%	$112.689	$112.69	$112.70	$112.70
Purchase #7	$242.85	10.199%	$267.6183	$267.62	$267.60	$267.60
7 purchase totals =	$1,207.74		$1,314.6004	$1,314.59	$1,314.55	$1,314.60