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	$127.29	12.127%	$142.7265	$142.73	$142.75	$142.70
Purchase #2	$161.55	3.765%	$167.6324	$167.63	$167.65	$167.60
Purchase #3	$239.61	4.713%	$250.9028	$250.90	$250.90	$250.90
Purchase #4	$51.54	4.414%	$53.815	$53.82	$53.80	$53.80
Purchase #5	$166.91	4.409%	$174.2691	$174.27	$174.25	$174.30
Purchase #6	$48.48	4.575%	$50.698	$50.70	$50.70	$50.70
Purchase #7	$147.54	8.573%	$160.1886	$160.19	$160.20	$160.20
7 purchase totals =	$942.92		$1,000.2324	$1,000.24	$1,000.25	$1,000.20