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	$130.61	9.815%	$143.4294	$143.43	$143.45	$143.40
Purchase #2	$194.94	13.736%	$221.717	$221.72	$221.70	$221.70
Purchase #3	$167.26	10.836%	$185.3843	$185.38	$185.40	$185.40
Purchase #4	$162.31	10.208%	$178.8786	$178.88	$178.90	$178.90
Purchase #5	$242.96	10.658%	$268.8547	$268.85	$268.85	$268.90
Purchase #6	$60.53	6.292%	$64.3385	$64.34	$64.35	$64.30
Purchase #7	$70.25	5.102%	$73.8342	$73.83	$73.85	$73.80
7 purchase totals =	$1,028.86		$1,136.4367	$1,136.43	$1,136.50	$1,136.40