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	$117.43	9.310%	$128.3627	$128.36	$128.35	$128.40
Purchase #2	$65.73	11.818%	$73.498	$73.50	$73.50	$73.50
Purchase #3	$81.49	9.392%	$89.1435	$89.14	$89.15	$89.10
Purchase #4	$156.44	11.404%	$174.2804	$174.28	$174.30	$174.30
Purchase #5	$14.49	9.419%	$15.8548	$15.85	$15.85	$15.90
Purchase #6	$196.41	10.350%	$216.7384	$216.74	$216.75	$216.70
Purchase #7	$29.61	9.867%	$32.5316	$32.53	$32.55	$32.50
7 purchase totals =	$661.60		$730.4094	$730.40	$730.45	$730.40