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	$175.88	11.856%	$196.7323	$196.73	$196.75	$196.70
Purchase #2	$168.56	10.703%	$186.601	$186.60	$186.60	$186.60
Purchase #3	$61.88	8.649%	$67.232	$67.23	$67.25	$67.20
Purchase #4	$95.84	7.348%	$102.8823	$102.88	$102.90	$102.90
Purchase #5	$5.47	12.458%	$6.1515	$6.15	$6.15	$6.20
Purchase #6	$175.91	8.179%	$190.2977	$190.30	$190.30	$190.30
Purchase #7	$38.25	10.386%	$42.2226	$42.22	$42.20	$42.20
7 purchase totals =	$721.79		$792.1194	$792.11	$792.15	$792.10