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	$184.50	3.701%	$191.3283	$191.33	$191.35	$191.30
Purchase #2	$45.46	8.266%	$49.2177	$49.22	$49.20	$49.20
Purchase #3	$248.31	8.244%	$268.7807	$268.78	$268.80	$268.80
Purchase #4	$89.52	7.622%	$96.3432	$96.34	$96.35	$96.30
Purchase #5	$52.57	12.391%	$59.0839	$59.08	$59.10	$59.10
Purchase #6	$123.28	8.658%	$133.9536	$133.95	$133.95	$134.00
Purchase #7	$202.39	7.499%	$217.5672	$217.57	$217.55	$217.60
7 purchase totals =	$946.03		$1,016.2746	$1,016.27	$1,016.30	$1,016.30