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	$151.72	5.564%	$160.1617	$160.16	$160.15	$160.20
Purchase #2	$156.71	7.652%	$168.7014	$168.70	$168.70	$168.70
Purchase #3	$239.36	5.174%	$251.7445	$251.74	$251.75	$251.70
Purchase #4	$68.92	13.803%	$78.433	$78.43	$78.45	$78.40
Purchase #5	$174.79	12.623%	$196.8537	$196.85	$196.85	$196.90
Purchase #6	$133.85	10.358%	$147.7142	$147.71	$147.70	$147.70
Purchase #7	$103.73	5.523%	$109.459	$109.46	$109.45	$109.50
7 purchase totals =	$1,029.08		$1,113.0675	$1,113.05	$1,113.05	$1,113.10