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	$99.46	10.285%	$109.6895	$109.69	$109.70	$109.70
Purchase #2	$72.61	5.648%	$76.711	$76.71	$76.70	$76.70
Purchase #3	$92.25	12.764%	$104.0248	$104.02	$104.00	$104.00
Purchase #4	$103.40	11.762%	$115.5619	$115.56	$115.55	$115.60
Purchase #5	$42.81	5.716%	$45.257	$45.26	$45.25	$45.30
Purchase #6	$186.32	3.789%	$193.3797	$193.38	$193.40	$193.40
Purchase #7	$188.88	13.435%	$214.256	$214.26	$214.25	$214.30
7 purchase totals =	$785.73		$858.8799	$858.88	$858.85	$859.00