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	$154.42	8.321%	$167.2693	$167.27	$167.25	$167.30
Purchase #2	$7.39	12.362%	$8.3036	$8.30	$8.30	$8.30
Purchase #3	$226.88	8.360%	$245.8472	$245.85	$245.85	$245.80
Purchase #4	$207.38	10.297%	$228.7339	$228.73	$228.75	$228.70
Purchase #5	$225.56	7.392%	$242.2334	$242.23	$242.25	$242.20
Purchase #6	$127.41	3.450%	$131.8056	$131.81	$131.80	$131.80
Purchase #7	$41.57	3.278%	$42.9327	$42.93	$42.95	$42.90
7 purchase totals =	$990.61		$1,067.1257	$1,067.12	$1,067.15	$1,067.00