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	$177.55	11.807%	$198.5133	$198.51	$198.50	$198.50
Purchase #2	$61.27	13.658%	$69.6383	$69.64	$69.65	$69.60
Purchase #3	$35.96	3.850%	$37.3445	$37.34	$37.35	$37.30
Purchase #4	$152.36	7.736%	$164.1466	$164.15	$164.15	$164.10
Purchase #5	$238.30	12.426%	$267.9112	$267.91	$267.90	$267.90
Purchase #6	$18.37	12.267%	$20.6234	$20.62	$20.60	$20.60
Purchase #7	$67.83	7.222%	$72.7287	$72.73	$72.75	$72.70
7 purchase totals =	$751.64		$830.9060	$830.90	$830.90	$830.70