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	$187.71	4.497%	$196.1513	$196.15	$196.15	$196.20
Purchase #2	$91.33	11.608%	$101.9316	$101.93	$101.95	$101.90
Purchase #3	$31.69	11.467%	$35.3239	$35.32	$35.30	$35.30
Purchase #4	$170.83	9.607%	$187.2416	$187.24	$187.25	$187.20
Purchase #5	$151.92	7.856%	$163.8548	$163.85	$163.85	$163.90
Purchase #6	$182.54	8.672%	$198.3699	$198.37	$198.35	$198.40
Purchase #7	$200.64	12.848%	$226.4182	$226.42	$226.40	$226.40
7 purchase totals =	$1,016.66		$1,109.2913	$1,109.28	$1,109.25	$1,109.30