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	$201.93	10.800%	$223.7384	$223.74	$223.75	$223.70
Purchase #2	$101.57	3.415%	$105.0386	$105.04	$105.05	$105.00
Purchase #3	$162.45	4.849%	$170.3272	$170.33	$170.35	$170.30
Purchase #4	$185.96	5.528%	$196.2399	$196.24	$196.25	$196.20
Purchase #5	$234.55	6.657%	$250.164	$250.16	$250.15	$250.20
Purchase #6	$40.41	6.789%	$43.1534	$43.15	$43.15	$43.20
Purchase #7	$76.60	4.687%	$80.1902	$80.19	$80.20	$80.20
7 purchase totals =	$1,003.47		$1,068.8517	$1,068.85	$1,068.90	$1,068.80