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	$243.57	10.636%	$269.4761	$269.48	$269.50	$269.50
Purchase #2	$72.91	3.757%	$75.6492	$75.65	$75.65	$75.60
Purchase #3	$72.58	3.761%	$75.3097	$75.31	$75.30	$75.30
Purchase #4	$190.37	3.190%	$196.4428	$196.44	$196.45	$196.40
Purchase #5	$69.69	13.104%	$78.8222	$78.82	$78.80	$78.80
Purchase #6	$156.63	6.816%	$167.3059	$167.31	$167.30	$167.30
Purchase #7	$55.60	7.535%	$59.7895	$59.79	$59.80	$59.80
7 purchase totals =	$861.35		$922.7954	$922.80	$922.80	$922.70