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	$240.37	5.314%	$253.1433	$253.14	$253.15	$253.10
Purchase #2	$103.97	8.330%	$112.6307	$112.63	$112.65	$112.60
Purchase #3	$65.81	10.789%	$72.9102	$72.91	$72.90	$72.90
Purchase #4	$167.73	13.258%	$189.9676	$189.97	$189.95	$190.00
Purchase #5	$78.80	5.696%	$83.2884	$83.29	$83.30	$83.30
Purchase #6	$192.38	12.609%	$216.6372	$216.64	$216.65	$216.60
Purchase #7	$86.76	5.187%	$91.2602	$91.26	$91.25	$91.30
7 purchase totals =	$935.82		$1,019.8376	$1,019.84	$1,019.85	$1,019.80