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	$106.52	10.809%	$118.0337	$118.03	$118.05	$118.00
Purchase #2	$235.53	5.710%	$248.9788	$248.98	$249.00	$249.00
Purchase #3	$27.25	4.263%	$28.4117	$28.41	$28.40	$28.40
Purchase #4	$70.41	11.244%	$78.3269	$78.33	$78.35	$78.30
Purchase #5	$133.71	9.284%	$146.1236	$146.12	$146.10	$146.10
Purchase #6	$203.81	9.280%	$222.7236	$222.72	$222.70	$222.70
Purchase #7	$47.75	4.426%	$49.8634	$49.86	$49.85	$49.90
7 purchase totals =	$824.98		$892.4617	$892.45	$892.45	$892.40