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	$191.57	3.607%	$198.4799	$198.48	$198.50	$198.50
Purchase #2	$26.82	3.644%	$27.7973	$27.80	$27.80	$27.80
Purchase #3	$190.75	12.347%	$214.3019	$214.30	$214.30	$214.30
Purchase #4	$131.51	3.839%	$136.5587	$136.56	$136.55	$136.60
Purchase #5	$146.38	12.304%	$164.3906	$164.39	$164.40	$164.40
Purchase #6	$190.62	3.195%	$196.7103	$196.71	$196.70	$196.70
Purchase #7	$64.88	11.479%	$72.3276	$72.33	$72.35	$72.30
7 purchase totals =	$942.53		$1,010.5663	$1,010.57	$1,010.60	$1,010.60