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	$68.72	4.476%	$71.7959	$71.80	$71.80	$71.80
Purchase #2	$67.57	3.762%	$70.112	$70.11	$70.10	$70.10
Purchase #3	$27.59	10.384%	$30.4549	$30.45	$30.45	$30.50
Purchase #4	$237.96	6.578%	$253.613	$253.61	$253.60	$253.60
Purchase #5	$56.58	4.724%	$59.2528	$59.25	$59.25	$59.30
Purchase #6	$240.34	11.751%	$268.5824	$268.58	$268.60	$268.60
Purchase #7	$232.26	5.735%	$245.5801	$245.58	$245.60	$245.60
7 purchase totals =	$931.02		$999.3911	$999.38	$999.40	$999.50