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	$199.88	9.756%	$219.3803	$219.38	$219.40	$219.40
Purchase #2	$92.91	5.838%	$98.3341	$98.33	$98.35	$98.30
Purchase #3	$206.41	9.355%	$225.7197	$225.72	$225.70	$225.70
Purchase #4	$120.25	10.636%	$133.0398	$133.04	$133.05	$133.00
Purchase #5	$159.74	5.741%	$168.9107	$168.91	$168.90	$168.90
Purchase #6	$106.32	9.615%	$116.5427	$116.54	$116.55	$116.50
Purchase #7	$127.77	11.424%	$142.3664	$142.37	$142.35	$142.40
7 purchase totals =	$1,013.28		$1,104.2937	$1,104.29	$1,104.30	$1,104.20