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	$180.90	5.571%	$190.9779	$190.98	$191.00	$191.00
Purchase #2	$201.40	3.440%	$208.3282	$208.33	$208.35	$208.30
Purchase #3	$39.93	7.572%	$42.9535	$42.95	$42.95	$43.00
Purchase #4	$90.95	7.816%	$98.0587	$98.06	$98.05	$98.10
Purchase #5	$127.31	12.753%	$143.5458	$143.55	$143.55	$143.50
Purchase #6	$159.99	11.309%	$178.0833	$178.08	$178.10	$178.10
Purchase #7	$140.86	7.741%	$151.764	$151.76	$151.75	$151.80
7 purchase totals =	$941.34		$1,013.7114	$1,013.71	$1,013.75	$1,013.80