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	$63.81	9.440%	$69.8337	$69.83	$69.85	$69.80
Purchase #2	$243.37	8.617%	$264.3412	$264.34	$264.35	$264.30
Purchase #3	$228.84	8.576%	$248.4653	$248.47	$248.45	$248.50
Purchase #4	$105.36	10.413%	$116.3311	$116.33	$116.35	$116.30
Purchase #5	$181.65	5.629%	$191.8751	$191.88	$191.90	$191.90
Purchase #6	$114.79	5.485%	$121.0862	$121.09	$121.10	$121.10
Purchase #7	$92.73	7.159%	$99.3685	$99.37	$99.35	$99.40
7 purchase totals =	$1,030.55		$1,111.3011	$1,111.31	$1,111.35	$1,111.30