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	$150.33	5.671%	$158.8552	$158.86	$158.85	$158.90
Purchase #2	$59.87	7.635%	$64.4411	$64.44	$64.45	$64.40
Purchase #3	$71.90	13.456%	$81.5749	$81.57	$81.55	$81.60
Purchase #4	$241.56	3.572%	$250.1885	$250.19	$250.20	$250.20
Purchase #5	$44.46	13.845%	$50.6155	$50.62	$50.60	$50.60
Purchase #6	$196.80	4.745%	$206.1382	$206.14	$206.15	$206.10
Purchase #7	$181.88	5.841%	$192.5036	$192.50	$192.50	$192.50
7 purchase totals =	$946.80		$1,004.3170	$1,004.32	$1,004.30	$1,004.30