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	$162.58	3.447%	$168.1841	$168.18	$168.20	$168.20
Purchase #2	$93.52	8.441%	$101.414	$101.41	$101.40	$101.40
Purchase #3	$27.84	13.830%	$31.6903	$31.69	$31.70	$31.70
Purchase #4	$37.91	11.242%	$42.1718	$42.17	$42.15	$42.20
Purchase #5	$225.50	13.780%	$256.5739	$256.57	$256.55	$256.60
Purchase #6	$227.72	13.542%	$258.5578	$258.56	$258.55	$258.60
Purchase #7	$173.89	11.671%	$194.1847	$194.18	$194.20	$194.20
7 purchase totals =	$948.96		$1,052.7766	$1,052.76	$1,052.75	$1,052.90