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	$47.63	11.824%	$53.2618	$53.26	$53.25	$53.30
Purchase #2	$167.46	3.850%	$173.9072	$173.91	$173.90	$173.90
Purchase #3	$87.25	3.443%	$90.254	$90.25	$90.25	$90.30
Purchase #4	$227.80	11.661%	$254.3638	$254.36	$254.35	$254.40
Purchase #5	$109.25	6.551%	$116.407	$116.41	$116.40	$116.40
Purchase #6	$157.82	6.235%	$167.6601	$167.66	$167.65	$167.70
Purchase #7	$39.62	12.764%	$44.6771	$44.68	$44.70	$44.70
7 purchase totals =	$836.83		$900.5310	$900.53	$900.50	$900.70