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	$235.34	12.540%	$264.8516	$264.85	$264.85	$264.90
Purchase #2	$71.25	13.450%	$80.8331	$80.83	$80.85	$80.80
Purchase #3	$86.39	11.486%	$96.3128	$96.31	$96.30	$96.30
Purchase #4	$136.67	6.293%	$145.2706	$145.27	$145.25	$145.30
Purchase #5	$149.48	6.728%	$159.537	$159.54	$159.55	$159.50
Purchase #6	$155.60	13.373%	$176.4084	$176.41	$176.40	$176.40
Purchase #7	$196.59	6.850%	$210.0564	$210.06	$210.05	$210.10
7 purchase totals =	$1,031.32		$1,133.2699	$1,133.27	$1,133.25	$1,133.30