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	$150.27	6.841%	$160.55	$160.55	$160.55	$160.60
Purchase #2	$96.83	11.871%	$108.3247	$108.32	$108.30	$108.30
Purchase #3	$139.52	4.675%	$146.0426	$146.04	$146.05	$146.00
Purchase #4	$215.56	11.696%	$240.7719	$240.77	$240.75	$240.80
Purchase #5	$114.64	13.525%	$130.1451	$130.15	$130.15	$130.10
Purchase #6	$110.99	11.444%	$123.6917	$123.69	$123.70	$123.70
Purchase #7	$176.52	4.542%	$184.5375	$184.54	$184.55	$184.50
7 purchase totals =	$1,004.33		$1,094.0635	$1,094.06	$1,094.05	$1,094.00