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	$105.33	4.513%	$110.0835	$110.08	$110.10	$110.10
Purchase #2	$19.53	5.124%	$20.5307	$20.53	$20.55	$20.50
Purchase #3	$73.44	6.636%	$78.3135	$78.31	$78.30	$78.30
Purchase #4	$244.59	11.437%	$272.5638	$272.56	$272.55	$272.60
Purchase #5	$104.43	6.520%	$111.2388	$111.24	$111.25	$111.20
Purchase #6	$146.74	11.519%	$163.643	$163.64	$163.65	$163.60
Purchase #7	$174.44	9.702%	$191.3642	$191.36	$191.35	$191.40
7 purchase totals =	$868.50		$947.7375	$947.72	$947.75	$947.70