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	$166.44	4.693%	$174.251	$174.25	$174.25	$174.30
Purchase #2	$88.63	4.555%	$92.6671	$92.67	$92.65	$92.70
Purchase #3	$148.87	12.375%	$167.2927	$167.29	$167.30	$167.30
Purchase #4	$164.45	5.240%	$173.0672	$173.07	$173.05	$173.10
Purchase #5	$168.77	3.799%	$175.1816	$175.18	$175.20	$175.20
Purchase #6	$61.72	9.850%	$67.7994	$67.80	$67.80	$67.80
Purchase #7	$111.55	10.352%	$123.0977	$123.10	$123.10	$123.10
7 purchase totals =	$910.43		$973.3567	$973.36	$973.35	$973.50