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	$113.84	4.140%	$118.553	$118.55	$118.55	$118.60
Purchase #2	$129.31	10.279%	$142.6018	$142.60	$142.60	$142.60
Purchase #3	$202.87	13.172%	$229.592	$229.59	$229.60	$229.60
Purchase #4	$43.58	5.284%	$45.8828	$45.88	$45.90	$45.90
Purchase #5	$20.60	9.634%	$22.5846	$22.58	$22.60	$22.60
Purchase #6	$149.30	7.403%	$160.3527	$160.35	$160.35	$160.40
Purchase #7	$47.25	13.448%	$53.6042	$53.60	$53.60	$53.60
7 purchase totals =	$706.75		$773.1711	$773.15	$773.20	$773.30