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	$96.69	8.576%	$104.9821	$104.98	$105.00	$105.00
Purchase #2	$120.77	5.369%	$127.2541	$127.25	$127.25	$127.30
Purchase #3	$134.54	7.713%	$144.9171	$144.92	$144.90	$144.90
Purchase #4	$83.78	7.777%	$90.2956	$90.30	$90.30	$90.30
Purchase #5	$207.38	11.498%	$231.2246	$231.22	$231.20	$231.20
Purchase #6	$80.61	9.621%	$88.3655	$88.37	$88.35	$88.40
Purchase #7	$205.75	8.836%	$223.9301	$223.93	$223.95	$223.90
7 purchase totals =	$929.52		$1,010.9691	$1,010.97	$1,010.95	$1,011.00