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	$184.90	3.786%	$191.9003	$191.90	$191.90	$191.90
Purchase #2	$137.92	13.184%	$156.1034	$156.10	$156.10	$156.10
Purchase #3	$163.77	13.146%	$185.2992	$185.30	$185.30	$185.30
Purchase #4	$183.98	7.684%	$198.117	$198.12	$198.10	$198.10
Purchase #5	$77.72	8.645%	$84.4389	$84.44	$84.45	$84.40
Purchase #6	$117.41	8.559%	$127.4591	$127.46	$127.45	$127.50
Purchase #7	$249.90	4.492%	$261.1255	$261.13	$261.15	$261.10
7 purchase totals =	$1,115.60		$1,204.4434	$1,204.45	$1,204.45	$1,204.40