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	$238.88	6.696%	$254.8754	$254.88	$254.90	$254.90
Purchase #2	$199.26	6.670%	$212.5506	$212.55	$212.55	$212.60
Purchase #3	$72.61	8.377%	$78.6925	$78.69	$78.70	$78.70
Purchase #4	$155.44	5.535%	$164.0436	$164.04	$164.05	$164.00
Purchase #5	$218.33	11.696%	$243.8659	$243.87	$243.85	$243.90
Purchase #6	$56.78	8.560%	$61.6404	$61.64	$61.65	$61.60
Purchase #7	$98.25	3.466%	$101.6553	$101.66	$101.65	$101.70
7 purchase totals =	$1,039.55		$1,117.3237	$1,117.33	$1,117.35	$1,117.40