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	$143.71	7.543%	$154.55	$154.55	$154.55	$154.60
Purchase #2	$86.41	11.686%	$96.5079	$96.51	$96.50	$96.50
Purchase #3	$195.39	10.175%	$215.2709	$215.27	$215.25	$215.30
Purchase #4	$29.72	4.751%	$31.132	$31.13	$31.15	$31.10
Purchase #5	$244.36	11.103%	$271.4913	$271.49	$271.50	$271.50
Purchase #6	$154.76	10.529%	$171.0547	$171.05	$171.05	$171.10
Purchase #7	$106.94	9.816%	$117.4372	$117.44	$117.45	$117.40
7 purchase totals =	$961.29		$1,057.4440	$1,057.44	$1,057.45	$1,057.50