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	$167.86	7.598%	$180.614	$180.61	$180.60	$180.60
Purchase #2	$164.96	4.636%	$172.6075	$172.61	$172.60	$172.60
Purchase #3	$48.56	11.791%	$54.2857	$54.29	$54.30	$54.30
Purchase #4	$94.91	6.715%	$101.2832	$101.28	$101.30	$101.30
Purchase #5	$181.64	5.339%	$191.3378	$191.34	$191.35	$191.30
Purchase #6	$185.72	3.415%	$192.0623	$192.06	$192.05	$192.10
Purchase #7	$77.75	13.238%	$88.0425	$88.04	$88.05	$88.00
7 purchase totals =	$921.40		$980.2330	$980.23	$980.25	$980.20