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	$57.63	10.809%	$63.8592	$63.86	$63.85	$63.90
Purchase #2	$150.49	10.534%	$166.3426	$166.34	$166.35	$166.30
Purchase #3	$134.73	11.552%	$150.294	$150.29	$150.30	$150.30
Purchase #4	$73.93	11.323%	$82.3011	$82.30	$82.30	$82.30
Purchase #5	$90.99	11.599%	$101.5439	$101.54	$101.55	$101.50
Purchase #6	$168.79	9.781%	$185.2993	$185.30	$185.30	$185.30
Purchase #7	$203.59	9.608%	$223.1509	$223.15	$223.15	$223.20
7 purchase totals =	$880.15		$972.7910	$972.78	$972.80	$972.80