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	$161.73	3.454%	$167.3162	$167.32	$167.30	$167.30
Purchase #2	$233.64	12.623%	$263.1324	$263.13	$263.15	$263.10
Purchase #3	$198.34	10.628%	$219.4196	$219.42	$219.40	$219.40
Purchase #4	$38.80	11.434%	$43.2364	$43.24	$43.25	$43.20
Purchase #5	$56.30	7.383%	$60.4566	$60.46	$60.45	$60.50
Purchase #6	$64.84	13.595%	$73.655	$73.66	$73.65	$73.70
Purchase #7	$250.40	5.454%	$264.0568	$264.06	$264.05	$264.10
7 purchase totals =	$1,004.05		$1,091.2730	$1,091.29	$1,091.25	$1,091.30