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	$176.83	3.446%	$182.9236	$182.92	$182.90	$182.90
Purchase #2	$243.31	9.687%	$266.8794	$266.88	$266.90	$266.90
Purchase #3	$57.36	8.558%	$62.2689	$62.27	$62.25	$62.30
Purchase #4	$136.29	3.694%	$141.3246	$141.32	$141.30	$141.30
Purchase #5	$119.92	12.810%	$135.2818	$135.28	$135.30	$135.30
Purchase #6	$179.83	4.758%	$188.3863	$188.39	$188.40	$188.40
Purchase #7	$156.77	11.294%	$174.4756	$174.48	$174.50	$174.50
7 purchase totals =	$1,070.31		$1,151.5402	$1,151.54	$1,151.55	$1,151.60