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	$189.76	3.453%	$196.3124	$196.31	$196.30	$196.30
Purchase #2	$164.33	9.103%	$179.289	$179.29	$179.30	$179.30
Purchase #3	$79.68	5.129%	$83.7668	$83.77	$83.75	$83.80
Purchase #4	$13.31	13.292%	$15.0792	$15.08	$15.10	$15.10
Purchase #5	$159.51	7.506%	$171.4828	$171.48	$171.50	$171.50
Purchase #6	$84.93	13.360%	$96.2766	$96.28	$96.30	$96.30
Purchase #7	$188.50	3.297%	$194.7148	$194.71	$194.70	$194.70
7 purchase totals =	$880.02		$936.9216	$936.92	$936.95	$937.00