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	$197.96	4.507%	$206.8821	$206.88	$206.90	$206.90
Purchase #2	$186.91	8.818%	$203.3917	$203.39	$203.40	$203.40
Purchase #3	$79.62	12.482%	$89.5582	$89.56	$89.55	$89.60
Purchase #4	$69.98	3.289%	$72.2816	$72.28	$72.30	$72.30
Purchase #5	$176.85	12.234%	$198.4858	$198.49	$198.50	$198.50
Purchase #6	$142.64	9.767%	$156.5716	$156.57	$156.55	$156.60
Purchase #7	$45.71	5.287%	$48.1267	$48.13	$48.15	$48.10
7 purchase totals =	$899.67		$975.2977	$975.30	$975.35	$975.40