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	$67.66	9.165%	$73.861	$73.86	$73.85	$73.90
Purchase #2	$47.51	11.669%	$53.0539	$53.05	$53.05	$53.10
Purchase #3	$59.44	9.821%	$65.2776	$65.28	$65.30	$65.30
Purchase #4	$109.84	12.216%	$123.2581	$123.26	$123.25	$123.30
Purchase #5	$147.80	13.706%	$168.0575	$168.06	$168.05	$168.10
Purchase #6	$86.73	11.102%	$96.3588	$96.36	$96.35	$96.40
Purchase #7	$210.79	13.159%	$238.5279	$238.53	$238.55	$238.50
7 purchase totals =	$729.77		$818.3948	$818.40	$818.40	$818.60