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	$94.54	3.805%	$98.1372	$98.14	$98.15	$98.10
Purchase #2	$211.78	3.188%	$218.5315	$218.53	$218.55	$218.50
Purchase #3	$20.60	4.281%	$21.4819	$21.48	$21.50	$21.50
Purchase #4	$191.61	6.788%	$204.6165	$204.62	$204.60	$204.60
Purchase #5	$54.61	8.835%	$59.4348	$59.43	$59.45	$59.40
Purchase #6	$238.71	13.307%	$270.4751	$270.48	$270.50	$270.50
Purchase #7	$207.67	13.319%	$235.3296	$235.33	$235.35	$235.30
7 purchase totals =	$1,019.52		$1,108.0066	$1,108.01	$1,108.10	$1,107.90