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	$207.96	9.490%	$227.6954	$227.70	$227.70	$227.70
Purchase #2	$36.29	8.689%	$39.4432	$39.44	$39.45	$39.40
Purchase #3	$99.35	12.131%	$111.4021	$111.40	$111.40	$111.40
Purchase #4	$142.58	9.412%	$155.9996	$156.00	$156.00	$156.00
Purchase #5	$91.54	7.734%	$98.6197	$98.62	$98.60	$98.60
Purchase #6	$176.74	8.255%	$191.3299	$191.33	$191.35	$191.30
Purchase #7	$176.75	4.728%	$185.1067	$185.11	$185.10	$185.10
7 purchase totals =	$931.21		$1,009.5966	$1,009.60	$1,009.60	$1,009.50