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	$174.99	9.178%	$191.0506	$191.05	$191.05	$191.10
Purchase #2	$56.87	12.709%	$64.0976	$64.10	$64.10	$64.10
Purchase #3	$64.60	7.658%	$69.5471	$69.55	$69.55	$69.50
Purchase #4	$197.60	7.354%	$212.1315	$212.13	$212.15	$212.10
Purchase #5	$173.26	13.663%	$196.9325	$196.93	$196.95	$196.90
Purchase #6	$94.59	9.860%	$103.9166	$103.92	$103.90	$103.90
Purchase #7	$164.27	3.432%	$169.9077	$169.91	$169.90	$169.90
7 purchase totals =	$926.18		$1,007.5836	$1,007.59	$1,007.60	$1,007.50